Re:barbouri babies

#4838
Pete Giwojna
Guest

Dear Lucy:

Outstanding! Thanks for the update!

You have had excellent success with your Hippocampus barbouri fry if you have been able to raise 70 of them to the three-month mark and wean them onto frozen Mysis successfully. A length of 3 inches at an age of three months indicates a very good growth rate for the juveniles.

As you know, the Brazilian seahorse (Hippocampus reidi) is notoriously difficult to rear because of its need for small live foods such as rotifers or larval copepods initially, combined with a lengthy pelagic phase of development. The fact that you have also raised some of your H. reidi juveniles to the age of three months and successfully weaned them onto frozen Mysis is also an outstanding achievement.

As I recall, you are planning on using ZM Fry Food (ZM Fish Food & Fishroom Equipment, a.k.a. Zebrafish Management Ltd., based in the UK) for raising your baby barbs and H. reidi, Lucy.

The ZM Fry Food is semi-buoyant when first added to the aquarium so that it stays suspended in the water column longer and simulates live foods. The ZM Fry Food includes shrimp meal which acts as a odor attracted to help stimulate a strong feeding response, as well as stabilized Vitamin C & Vitamin B-12. And the ZM Fry Food is that it’s available in a number of different particle sizes, which are suitable for fry at different stages of development.

For example, the ZM-000 Fry Food has particles that are less than 90 microns in diameter and can be used as an alternative or supplement to live rotifers for fry that are too small to accept newly brine shrimp, such as your H. reidi fry.

Likewise, the ZM-100 Fry Food has particles from 80-200 microns, making them a little smaller than most newly hatched brine shrimp. That would make them a possible alternative or supplement for newly hatched brine shrimp (1st instar Artemia nauplii).

The ZM-200 Fry Food (150-200 microns) is similar in size to newly hatched brine shrimp, and can be used as a substitute for Artemia for fry that are a little larger and ready to accept 2nd instar brine shrimp.

And the ZM-300 Fry Food (300-500 microns) could be offered to the juveniles when they are ready for slightly larger food, and so on.

If seahorse fry will actually accept the ZM Fry Food, that would be a tremendous boon for seahorse keepers, especially the home breeders. Offering these particle foods to the newborns and young seahorses would be much more economical and convenient, sparing the hobbyist from the hassle of culturing rotifers and copepods or preparing copious amounts of newly hatched brine shrimp on a daily basis. So please keep us informed on the progress of your H. reidi and H. barbouri juveniles and how well they are eating the ZM Fry Food, Lucy.

Thank you very much for bringing this easy alternative to our attention — this is a very exciting development if the seahorse fry readily eat the dry foods and show good growth and survivorship on such a diet.

I believe I speak for all of the members on this forum when I say that we would be very grateful if you can share with us some details of how you use the ZM Fry Food with such outstanding success with your H. barbouri and H. reidi fry, Lucy! Can you briefly outline for us what sort of feeding regimen you used, including which of the ZM fry food you used when the fry were at various ages and stages of development? Did you use any of the traditional live foods (e.g., copepods, rotifers, newly hatched brine shrimp) when raising your fry, and then supplement their diet with the ZM Fry Food, or where you relying strictly on the ZM Fry Food of the proper size as the staple diet for the newborns and juveniles until they were weaned onto frozen foods? We would all appreciate some more information on how you managed to achieve your outstanding rearing success, Lucy!

Regarding your disease treatment question, when you say that your friend has a problem with "white spot" in his seahorse tank, I assume you mean that he is dealing with an outbreak of Cryptocaryon irritans. As you know, Cryptocaryon is commonly known as saltwater ich or white spot disease. It is caused by a ciliated protozoan parasite that burrows into the skin and gills of its host and is one of the most common diseases of marine fishes. Most hobbyists who keep saltwater fish are all too familiar with Cryptocaryon. In the confines of the aquarium, massive reinfestation with these parasites occurs, making Cryptocaryon deadly if left untreated.

In seahorses, it often occurs as a masked infection. The bony exoskeleton and protective slime coat of Hippocampus gives the seahorse limited immunity from the burrowing trophonts, so the telltale white spots may never show up (or may be visible only on the unarmored fins). But the parasites can still freely invade the seahorse’s gills, with deadly results.

Here is an excerpt from my new book (Complete Guide to the Greater Seahorses in the Aquarium, unpublished) that discusses the symptoms and treatment options for Cryptocaryon irritans in more detail:

<open quote>
Cryptocaryon irritans (Saltwater Ich, a.k.a. White Spot Disease)

Cryptocaryon is another protozoal parasite that invades the gills and burrows into the skin of marine fishes, including seahorses. The life cycle and modus operandi of Cryptocaryon are very similar to that of Amyloodinium ocellatum, so it should not be surprising that it also produces strikingly similar symptoms. Infected fish show labored breathing, excess mucus, and scratch themselves against objects. Along with the characteristic pinhead-sized white spots and excess mucus production, affected fish sometimes show cloudy eyes and secondary infections (Basleer, 2000). The latter can result in skin rot and fin rot accompanied by red or pale patches on the body of the fish (Basleer, 2000).

The white spots seen on infected fish are the adult stage of the parasite, known as trophonts (Basleer, 2000). When they mature, they fall off the fish and encyst themselves. The encapsulated parasites are known as tomonts (Basleer, 2000). Well protected within these cysts, the tomont stage cannot be killed by any medications. The encapsulated tomonts divide into hundreds of daughter cells, which develop into small, ciliated, free-swimming parasites, called tomites (Basleer, 2000). When the cysts rupture, the motile tomites swarm out to seek a new host. In the aquarium, they reinfect the same fishes, and bore into the mucosa of the skin, gills, and fins of their hapless hosts. Once embedded in the tissue, they mature into typical trophonts, appearing as pinhead-sized white spots on most fish, and start the cycle of infection all over again (Basleer, 2000). It is these heavy infestations that can overwhelm even healthy fish.

The free-swimming stage of their life cycle is Cryptocaryon’s one great weakness. The motile tomites are vulnerable and exposed. Ozone or UV can destroy them, they can be killed by all the usual chemotherapeutic agents, and they explode (lyse) when exposed to freshwater and low salinity. It is therefore the tomites that the aquarist must target when treating Cryptocaryon.

At 100x magnification, Cryptocaryon parasites can easily be identified in skin and fin smears. They appear as large, dark, bell-shaped or conical organisms measuring about 350-400 micrometers in diameter (Basleer, 2000).

Outbreaks usually coincide with the introduction of new specimens or environmental insults such as rapid temperature fluctuations (heat stress or chilling), ammonia or nitrite spikes, or a sharp drop in pH (Basleer, 2000). The first step toward treating Cryptocaryon is therefore to restore water quality. Check your aquarium parameters and administer water changes as needed.

The traditional treatment is similar to that for Amyloodinium. Combination drugs such as formaldehyde/copper sulfate or formaldehyde/malachite green are often more effective than copper alone (Basleer, 2000). Medication must be maintained at therapeutic levels for at least 8-10 days and the best results are obtained when daily freshwater dips are a part of the treatment regimen (Basleer, 2000). The entire tank should be treated and methylene blue can be added to the water to aid the breathing of the fish (Basleer, 2000). Be aware that these medications will impair your biofilter and kill your invertebrates!

For this reason, hyposalinity or osmotic shock therapy (OST) is my preferred method for eradicating Cryptocaryon from a seahorse tank.

Cryptocaryon is normally easily distinguished from Amyloodinium by the fact that the embedded parasites produce pinhead sized white spots that are much larger that the tiny dust specks that indicate Marine Velvet. However, the telltale white spots are again often entirely absent when seahorses are the hosts, leaving the seahorse keeper in a quandary when it comes to diagnosis and treatment. <Close quote>

That’s the rundown on Cryptocaryon irritans, Lucy.

For best results, I recommend maintaining the hyposalinity for six to eight weeks to ensure that all of the encysted parasites have emerged and been killed by the osmotic shock therapy. After six to eight weeks, you can then very gradually return the aquarium to normal salinity over a period of two or more weeks.

Here are the instructions for administering hyposalinity or osmotic shock therapy safely:
Osmotic Shock Therapy (OST)
Hyposalinity or Osmotic Shock Therapy (OST) is a very safe treatment that is effective against protozoans and ectoparasites in general. OST is totally noninvasive and harmless to seahorses and most other fishes, can be administered safely in the display tank rather than a hospital tank to eradicate the protozoan parasites from your system, and is completely compatible with UV and any medications you may be using (Giwojna, Dec. 2003). OST is therefore the treatment I recommend for problems with external parasites other than Uronema.
Hyposalinity also helps parasite-ridden fish avoid dehydration and save their strength by reducing osmotic pressure and making it easier for them to osmoregulate. Allow me to explain.
Because the seawater they live in is far saltier than their blood and internal body fluids (Kollman, 1998), marine fish are constantly losing water by diffusion through their gills and the surface of their skin, as well as in their urine (Kollman, 1998). The mucus layer or slime coat of the fish helps waterproof the skin and reduces the amount of water that can diffuse through its surface (Kollman, 1998). However, when the skin is attacked by parasites such as Costia, Cryptocaryon, Cryptobia, Amyloodinium, Brooklynella, Epistylus and the like, this protective barrier is damaged and water is lost at an increasing rate (Kollman, 1998). The affected fish can easily become dehydrated as a result, further debilitating them.
Low salinity is an excellent way to treat most such skin infections, since reducing the salinity helps the fish recover in several different ways. It lessens the risk of dehydration by decreasing osmotic pressure (Kollman, 1998), and reduces the amount of energy the fish must expend on osmoregulation, helping the weakened fish to recover (Kollman, 1998).
And if the salinity is dropped far enough, it prevents reinfection and provides the fish with immediate relief by destroying the parasites in the water and on the surface of the skin (Kollman, 1998). At low salinity, water moves into the parasites’ bodies by passive diffusion until they literally burst (lyse). This method of treatment is known as hyposalinity or Osmotic Shock Therapy.
At the first sign of parasitic infection, I therefore suggest instituting a two-pronged treatment regimen immediately: (1) first, administer a freshwater dip to your seahorses to reduce the number of embedded parasites, clear the gills and snout as much as possible, and provide the seahorses with some quick relief, and (2) treat your main tank with osmotic shock therapy, dropping the salinity to 15 ppt (1.011-1.012) for several weeks to eliminate the parasites from your system entirely (Giwojna, Dec. 2003). If your seahorses seem too weak to handle the stress of a freshwater dip, then just get them into hyposalinity water ASAP — no acclimation!
Step 1: Freshwater Dip
Freshwater Dips

A freshwater dip is simply immersing your seahorse in pure, detoxified freshwater that’s been preadjusted to the same temp and pH as the water the seahorse is accustomed to, for a period of at least 10 minutes (Giwojna, Dec. 2003). It doesn’t harm them — seahorses typically tolerate freshwater dips exceptionally well and a 10-minute dip should be perfectly safe. Freshwater dips are effective because marine fish tolerate the immersion in freshwater far better than the external parasites they play host to; the change in osmotic pressure kills or incapacitates such microorganisms within 7-8 minutes (Giwojna, Dec. 2003). A minimum dip, if the fish seems to be doing fine, is therefore 8 minutes. Include some sort of hitching post in the dipping container and shoot for the full 10 minutes with your seahorses (Giwojna, Dec. 2003).

If you will be using tap water for the freshwater dip, be sure to dechlorinate it beforehand. This can be accomplished usually one of the commercial dechlorinators, which typically include sodium thiosulfate and perhaps a chloramine remover as well, or by aerating the tap water for at least 24 hours to dissipate the chlorine (Giwojna, Dec. 2003).

If you dechlorinate the dip water with a sodium thiosulfate product, be sure to use an airstone to aerate it for at least one hour before administering the dip. This is because the sodium thiosulfate depletes the water of oxygen and the dip water must therefore be oxygenated before its suitable for your seahorse(s). Regardless of how you detoxify the freshwater for the dip, it’s important to aerate the water in the dipping container well beforehand to increase the level of dissolved oxygen in the water. Many hobbyists leave the airstone in the dipping container throughout the procedure.

Adjusting the pH of the water in the dipping container so that it matches the pH of the water in the aquarium is a crucial step. Ordinary baking soda (sodium bicarbonate) will suffice for raising the pH of the water. If there is too much of a difference in the pH, there is a possibility the seahorse could go into shock during the dipping procedure. Preadjusting the pH will prevent that from happening. If you will are unsure about your ability to accurately adjust the pH in the dipping container, avoid this procedure altogether or be prepared to monitor the seahorse very carefully or shorten the duration of the tip to no more than about 4 minutes.

Observe the horse closely during the dip. You may see some immediate signs of distress or shock. Sometimes the horse will immediately lie on its side on the bottom. That’s a fairly common reaction — normal and to be expected, rather than a cause for concern, so don’t be alarmed if this happens. Just nudge or tap the seahorse gently with your finger if it lies down on its side. Normally, the seahorse will respond to the slight nudge by righting itself again and calm down for the duration of the dip. However, if it does not respond, stop the treatment.

Most seahorses tolerate the treatment well and experience no problems, but if you see continued signs of distress — twitching, thrashing around etc. — stop the treatment.

After you have completed the dip and returned the seahorses to the aquarium, save the dip water and examine it closely for any sign of parasites. The change in osmotic pressure from saltwater to freshwater will cause ectoparasites to lyse (i.e., swell and burst) or drop off their host after 7-10 minutes, and they will be left behind in the dipping water. Protozoan parasites are microscopic and won’t be visible to the naked eye, but some of the other ectoparasites can be clearly seen. For example, monogenetic trematodes will appear as opaque sesame seeds drifting in the water (Giwojna, Aug. 2003) and nematodes may be visible as tiny hairlike worms 1/16-3/16 of an inch long. Other parasites may appear as tiny dots in the water. Freshwater dips can thus often provide affected seahorses with some immediate relief by ridding them of these irritating pests and can also aid their breathing by flushing out gill parasites.

If you suspect a problem with parasites, the dip should be extended for the full 8-10 minutes if possible for best results.

Step 2: Hyposalinity (Osmotic Shock Therapy)
Osmotic Shock Therapy (OST) involves maintaining the saltwater in your system at a much lower specific gravity than normal: 1.017 is recommended for reef tanks with live coral and invertebrates, while 1.011 (15 ppt salinity) is appropriate for fish-only tanks (Giwojna, Dec. 2003). Essentially, OST simply places the infectious organisms in an environment in which they cannot hope to survive while the host (or infected fish) is unaffected (Hauter, 2004). It is therefore the parasites that are subjected to the shock, not the fishes, which are normally quite content at the prescribed salinities (Giwojna, Dec. 2003). This low salinity method can be thought of as a continuous freshwater dip, and provides basically the same benefits as a 5-10 minute freshwater dip does, only long term (Giwojna, Dec. 2003).
When the salinity in the system is lowered initially, it is done as if performing a normal water change, except that the replacement water is simply treated tap or RO water without the salt (Don Carner, pers. com.). (If the replacement water is RO/DI or other softened source, then a buffering agent should be employed to prevent pH and alkalinity drops; Thiel, 2003.) Make sure the freshwater you add is thoroughly mixed with the remaining saltwater in the tank as you proceed. This will assure that your salinity/specific gravity readings are accurate. Monitor the lowering closely so as to not reduce it too fast. Achieving the desired specific gravity (1.010-1.012) over a period of several hours is fine (Don Carner, pers. com.). The bacteria colony in the biofilter will survive, the fish will survive, but the parasites will not (Don Carner, pers. com.).
By lowering the salinity, we are also lowering the osmotic pressure of the water. The parasites NEED high osmotic pressure externally in order to maintain a normal water balance within their bodies (Don Carner, pers. com.). Reduce the salinity of the surrounding saltwater sufficiently, and water moves via osmosis into the parasites’ bodies until they literally explode (Giwojna, Dec. 2003). As a higher life form, the fish can withstand this treatment very well; invertebrates and parasites cannot (Don Carner, pers. com.).
For best results, I recommend removing your seahorses to a hospital tank or bucket filled with full strength saltwater (1.022-1.025) while dropping the salinity in the main tank. They can be given their freshwater dips while you are reducing the salinity in the main tank. Once the specific gravity in the display tank has been lowered to the desired level, the seahorses can then be released directly into the main tank without any acclimation whatsoever. They will make the transition from full strength saltwater to hyposalinity wonderful well, without missing a beat, whereas the ectoparasites they are carrying will be subjected to a lethal change in osmotic pressure.
Do not hesitate to maintain the hyposalinity for the entire treatment period. OST needs to maintained for at least 3 weeks, and a 6-8 week treatment period is advisable, in order to assure that all of the encysted parasites have reached the free-swimming stage of their life cycle and been killed.
CAUTION! When administering hyposalinity to seahorses, be very careful as you add the freshwater when you approach the target salinity. You do NOT want to overshoot the mark and drop the salinity too far! Seahorses tolerate low salinity very well up to a certain point, but they cannot withstand salinities below 13.3 ppt (specific gravity = 1.010) indefinitely. Salinities below 1.010 may be fatal to seahorses in a matter of days, if not hours.
In the olden days, many attempts were made to gradually convert seahorses from saltwater to freshwater. Hippocampus erectus tolerated these experiments splendidly all the way down to specific gravity of 1.010, but when the salinity was dropped any further, the seahorses all perished (Bellomy, 1969, p7). These experiments were repeated with several groups of seahorses representing different subspecies of erectus, and the results were always the same: fine as low as 1.010 — defunct at 1.009 (Bellomy, 1969, p7)!
Keeping that in mind, it is best to make your target salinity 1.011-1.012 to allow a margin for error, and to transfer your seahorses to a hospital tank while you drop the salinity in the main tank. That way no harm will be done if you accidentally take the salinity down too far in your main tank before readjusting it and hitting your target salinity. And when you return the seahorses from normal salinity in the hospital tank to the main tank at 1.011-1.012, the parasites will be subjected to the greatest possible osmotic shock, leaving them no chance at all to adjust to change in osmotic pressure.
To be safe and effective, administering hyposalinity requires the use of an accurate method for measuring salinity/specific gravity such as a refractometer. If you will be relying on a pet-store hydrometer for your readings, you may wish to consider alternate treatments rather than OST. If you do decide to try hyposalinity using a hydrometer, please observe the following precautions:
Be aware of the temperature at which your hydrometer was calibrated and make full use of conversion charts to adjust your readings based on the actual temperature of the water aquarium water.
Make your target salinity 20 ppt (specific gravity = 1.015) to allow for a greater margin for error.
In addition, when administering OST it is important to monitor your ammonia and nitrite levels closely at first. Hyposalinity may temporarily impact the nitrifying bacteria in your biofilter, so check your readings closely to see if there is a spike once you’ve reached your target salinity. If so, a simple water change will correct the problem and your biofiltration will be back to normal shortly.
The hobbyist should also bear in mind that hyposalinity can delay gonadal development in immature seahorses and may also prevent mature seahorses from breeding until the salinity is returned to normal. So don’t maintain low salinity for the long term — as soon as the 3-4 week treatment period is over, bring the specific gravity in the main tank back up 1.024-1.025.
When you are ready to return the system to normal salinity, simply reverse the process, remove some of the low salinity water in the aquarium and replace it with high salinity water. Take your time and raise the salinity slowly and gradually. Fish can become dehydrated if the salinity is increased too rapidly, so be methodical and raise the salinity over a period of weeks. Don’t hesitate to take two full weeks or more to return the specific gravity to normal levels again in small increments.
If your tank contains corals or delicate invertebrates, or you just want to be extra cautious with your seahorses as they recuperate, adjust the salinity more slowly. This can be accomplished by making smaller water changes, which will require more steps to raise the salinity back to normal, or by reducing the specific gravity of the high-salinity replacement water somewhat. Make the adjustment back to normal salinity as gradually as necessary in order to be confident that you are not stressing the specimens. The hyposalinity should already have done its job so you can afford to be cautious when readjusting the salinity. Take all the time you want.
To be absolutely certain that things go smoothly, take advantage of the online Salinity Adjustment Calculator at the following web site: <http://saltyzoo.com/SaltyCalcs/SalinityAdjust.php&gt;
This calculator takes the amount of water in your system, your current salinity, the salinity you’d like to achieve, and the maximum change in salinity that you are willing to risk per water change into consideration and performs the necessary calculations. It then returns the number of gallons and salinity of the water for each change (Taylor, 2001b).
The low salinity system was initially developed at the Instant Ocean Hatcheries in the 1980’s and has since been perfected by other large-scale operations (Giwojna, Dec. 2003). Thomas Frakes at Aquarium Systems recommends this system and Rand Kollman recently conducted a controlled study of the method, as described below (Kollman, 1998):
During the study, fourteen 40-gallon tanks connected to a common filtration system at Kollman’s dealership were run at 15 ppt salinity (specific gravity = 1.011), while sixteen other 30-gallon tanks, connected to their own separate filtration system, were maintained at normal salinities of 27-30 ppt (specific gravity = 1.020-1.022) and served as the control group for the experiment (Kollman, 1998; Giwojna, Dec. 2003). Both systems had identical filtration and were maintained at the same temperature (between 79-80 degrees F), Kollman, 1998.
The test period ran continuously from 1994 to 1997, during which time marine fish from the Red Sea, Caribbean and throughout the Indo-Pacific were maintained in both systems (Kollman, 1998). Whenever fish arrived from wholesalers or transshipments, they were divided evenly between the low salinity and the normal salinity (control) system with no acclimation procedures whatsoever (Kollman, 1998; Giwojna, Dec. 2003). No differences in behavior were observed between the fishes in the two systems during the trial period (Giwojna, Dec. 2003).
The results of the three-year study were dramatic and conclusive (Giwojna, Dec. 2003). Outbreaks of Amyloodinium, Cryptocaryon, turbellarians, and monogenetic trematodes were simply not seen in the low salinity system, and periodic microscopic examinations of skin scrapings and gill clippings confirmed that none of the parasites were present (Kollman, 1998; Giwojna, Dec. 2003). On the other hand, the normal salinity control system continued to have periodic outbreaks of all the above parasites. Furthermore, infected fish from the control system were cleared of their parasites within a few days if transferred to the low salinity system (Kollman, 1998; Giwojna, Dec. 2003).
Kollman found the low salinity system reduced his previously high mortality rates and that his dealership was able to greatly reduce chemical treatments and subsequent overdoses (Kollman, 1998; Giwojna, Dec. 2003). He concluded that a salinity of 14 to 15 ppt (specific gravity = 1.010-1.011) was an effective treatment level to which fish can be immediately transferred with no special acclimation procedures (Kollman, 1998; Giwojna, Dec. 2003). Although the rapid turnover of specimens at his dealership prevented him from reaching any definitive conclusions about the long-term effects of low salinity on marine fishes, Kollman noted that several fish were maintained in the system for well over a year with no ill effects, and that a Red Sea angelfish (Pomacanthus maculosus) thrived in the low salinity system for three-and-a-half years (Kollman, 1998; Giwojna, Dec. 2003)!
Kollman’s study and the ongoing program at Instant Ocean hatcheries are not the only reports on utilizing low salinity water to quarantine specimens held under crowded conditions (Giwojna, Dec. 2003). As early as 1985, Colorni published a study in Diseases of Aquatic Organism on the effectiveness of hyposalinity in controlling Cryptocaryon irritans in cultured sea bream (Colorni, 1985). Randolph Goodlett and Lance Ichinotsubo have likewise reported their own low-salinity treatment techniques, recommending at least 3 weeks exposure at 14 ppt (specific gravity = 1.010) for a broad range of marine tropical fish species to control various parasites (Goodlett and Ichinotsubo, 1997). They too reported that fish handled immediate transfer into low salinity water "beautifully (Goodlett and Ichinotsubo, 1997)." Variations of low salinity or OST are also gaining popularity among reefkeepers for curing disease outbreaks in reef tanks where copper and other medications cannot be used (Frakes, 1994; Giwojna, Dec. 2003).
Low Salinity Pros (Giwojna, Dec. 2003):
1. Less stressful and longer lasting than freshwater dipping.
2. More effective than freshwater dipping outside the aquaria, since OST kills the free swimming parasites as they emerge from dormant cysts/spores within the aquaria/system as well as those attached to the fish (i.e., the fish are not reinfected once they are returned from the bath to the main tank).
3. No special acclimation procedures required for newcomers.
4. Suitable for all marine teleost (bony) fishes (Red Sea, Indo-Pacific, Florida & Caribbean).
5. Seahorses tolerate hyposalinity extremely well.
6. Eliminates outbreaks of Cryptocaryon irritans (White Spot Disease/Marine Ick).
7. Eliminates turbellarians (Black Spot/Clownfish Disease).
8. Eliminates most ectoparasites, including trematodes, flukes, leeches and Argulus;
9. Prevents the spread of protozoal parasites in general.
10. Reduces the risk of dehydration when the integrity of the fish’ slime coat is disrupted;
11. Helps weakened fish conserve energy and husband their strength by lowering osmotic pressure and making it easier for them to osmoregulate.
12. Reduces dependency on chemical treatments such as copper and formalin.
13. Eliminates the risk of overdoses.
14. Proven to improve the health of marine teleost fishes kept in crowded containment systems with a heavy biological load.
15. Can be used safely with protein, skimmers, ozone, UV, and other treatments.
Low Salinity Cons (Giwojna, Dec. 2003):
1. Sharks and rays are unable to adjust to low salinity systems or tolerate OST.
2. Cannot be used with corals and invertebrates at salinities recommended for fishes.
3. Can be harmful to seahorses at salinities below 13.3 ppt (specific gravity = 1.010).
4. May delay gonadal development in seahorses and prevent breeding until the salinity is returned to normal.
5. Requires an accurate method for measuring salinity/specific gravity such as a refractometer for best results.
6. May not be helpful in cases of Uronema — the most common protozoan parasite infection in seahorses.
7. May impact nitrifying bacteria in the biofilter temporarily.
8. Not recommended for long-term maintenance (this will not be a concern for any fishes that are in the system for 6-8 weeks or less).
9. Results vary — many hobbyists report great success with hyposalinity; others have no luck using this technique. Much depends on how OST was administered, how low the salinity was reduced and how quickly it was dropped, the accuracy of the salinity measurements, the particular parasite(s) involved and how early treatment was begun.
Invertebrates differ in their tolerance for hyposalinity. Kollman notes that he was able to keep several crustaceans at a fairly low salinity of 18-19 ppt (specific gravity = 1.013 to 1.014). These included arrow crabs, peppermint shrimp, and emerald crabs (Kollman, 1998). Hermit crabs are generally perfectly happy undergoing OST, echinoderms (starfish and urchins) typically don’t tolerate it at all, most shrimp are sensitive, snails vary (Giwojna, Dec. 2003). Nerites and periwinkles don’t mind it at all, others are okay at 1.017 but you can kiss them goodbye at 1.010. Most corals are vulnerable to full OST (Giwojna, Dec. 2003). Reefkeepers and hobbyists with sensitive animals usually do a modified version of OST where they lower the salinity to 1.017 rather than 1.010 (Giwojna, Dec. 2003). The delicate animals generally tolerate 1.017 well and although that’s not as effective in eradicating parasites, a specific gravity of 1.017 is still low enough to provide many of the benefits of hyposalinity (Giwojna, Dec. 2003).
For a standard SHOWLR setup with a clean-up consisting of assorted snails, microhermits, and cleaner shrimp, I recommend relocating the snails and shrimp while treating your seahorse system with full OST at a specific 1.011-1.012 for several weeks. If that’s not practical because it would be too difficult to account for all the snails and/or shrimp and remove them, then I would suggest taking the salinity carefully down to about 1.017 in your main tank, which most of your janitors should tolerate just fine, after moving your seahorses to your hospital tank for treatment at full OST.
Just set up your hospital tank at a salinity of 15-16 ppt (a specific gravity of 1.011-1.012) and adjust the water to the same temp and pH as the main tank. Then administer a freshwater dip to your seahorses, and transfer them directly into the hyposalinity treatment tank afterwards without any acclimation whatsoever.
As I mentioned earlier, OST is completely compatible with most medications. (In fact, many medications are more effective at low salinity than they are in full strength saltwater.) Since secondary bacterial or fungal infections often accompany parasite problems, I would also recommend combining hyposalinity in the hospital tank with antibiotic therapy. In that case, simply medicating the hospital tank with the appropriate antibiotics will be easier than administering the antibiotics orally via gut-loaded shrimp. [CAUTION: if administering hyposalinity in your main tank, do not administer antibiotics, which may adversely impact the biofiltration in the aquarium.]
Nifurpirinol used in conjunction with neomycin will be very effective for medicating the hospital tank during OST, as will the powerful combination drugs that contain both antiprotozoal and wide-spectrum antibacterial agents. Look for a product that includes ingredients such as nitrofurazone and metronidazole, which are very effective against protozoan parasites, as well as antibiotics such as neomycin and kanamycin, which are powerful broad-spectrum medications.
If you do not see improvement within 4-5 days of administering OST, don’t hesitate to use the alternative treatments discussed for each particular parasite! They can be administered safely in conjunction with hyposalinity, bearing in mind the impact they will have on the biological filtration, or you can carefully return the salinity to normal and then treat with chemotherapeutics. When administering alternate treatments, check your ammonia/nitrite readings closely, and use water changes as needed to keep the levels of ammonia and nitrite at acceptable levels. Also, you are strongly advised to administer daily freshwater dips in addition to treating with chemotherapeutic agents if the alternative treatments are used in the absence of OST. The freshwater dips will provide the same benefits as hyposalinity and enhance the effectiveness of whatever treatment you employ to control the parasites.
Modified OST for Reef Tanks
Reefers generally run a modified version of OST in which they maintain a somewhat higher specific gravity, usually around 1.017 (Thiel, 2003), for a longer period of time in order to control protozoal parasites. Most corals are safe at even lower salinities, but 1.017 usually provides adequate protection and provides a margin for error. In any case, as a rule, reef keepers DO NOT take their systems lower than 1.015 for safety’s sake (Thiel, 2003). (This is also a good option for hobbyists who have only a typical pet-store hydrometer for measuring specific gravity, or anyone with many invertebrates in their seahorse setup.)
Corals typically close slightly immediately after the salinity is lowered, but are open fully again by the next day, and suffer no harmful long-term effects from hyposalinity at 1.017 whatsoever (Thiel, 2003). Reefers who practice OST report that it has no long-term detrimental effects on the growth rate of their corals.
According to Thiel, corals that are know to be sensitive to hyposalinity, and which are thus not well suited for OST, include Seriotopora hystrix, Montipora digitata, Pocillopora species and other similar hard corals with a fine, dense, polyp structure (Thiel, 2003). Acropora species, however, handle hyposalinity well and soft corals are also generally fine, including such sensitive softies as Xenia, Lemnalia, and the like (Thiel, 2003). As long as the pH and alkalinity are maintained at normal levels, most hard corals are not harmed at a specific gravity as low as 1.017.

Don’t return any sensitive invertebrates to the main tank until the entire regimen of hyposalinity has been completed and the aquarium has been returned to normal salinity again.

Okay, that’s the breakdown administering hyposalinity, Lucy!

Best of luck with your fine crop of juvenile seahorses!

Happy Trails!
Pete Giwojna


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