Nitrates

Dear Sean:

Thanks for the update! It’s great to hear that your ammonia levels are back down to zero in the main tank and that your new Mustangs are thriving despite the cramped quarters in your quarantine tank.

I wouldn’t expect to be seeing elevated nitrate levels in a new aquarium like yours with lots of live rock and a very light bioload, but nitrates can enter your system via some tricky routes, including through your tap water, and I suspect something like that may be happening in your case, sir. There are a number of things to keep in mind if you’re having a problem with nitrates, Sean, since they can enter your aquarium in some pretty sneaky ways that you may not suspect. Here’s a good discussion on controlling nitrates that you may also find helpful:

Nitrates in the Aquarium: Where They Come from and How to Control Them

In and of themselves, nitrates are relatively harmless and midrange levels are nothing to be too alarmed about. Normally a nitrate reading of 20 ppm is not a cause for concern with seahorses. Ideally, though, we’d like to keep them under 20 ppm at all times and below 10 ppm, it possible, and if your nitrates are running on the high side you’ll want to take measures to reduce them. In case you haven’t already seen it, I am going to provide you with some information on nitrification and denitrification that explains where nitrates come from and then offer you some suggestions on how to reduce them.

The amount of nitrate that accumulates in your aquarium is related to how much nitrification and denitrification your system provides. Nitrification is the process by which aerobic (oxygen loving) nitrifying bacteria break down toxic ammonia to relative harmless nitrate in a series of steps. Nitrification thus ultimately causes nitrate to build up in an aquarium. Denitrification is the process by which anaerobic (oxygen hating) denitrifying bacteria then convert nitrate into completely harmless nitrogen (N2), which eventually leaves the aquarium. Denitrification thus removes nitrate from your system. This entire process is known as the nitrogen cycle.

Cycling your aquarium simply means to build up a healthy population of beneficial bacteria in your tank that can carry out the nitrogen cycle and breakdown your fishes’ waste products. Ammonia (NH3), nitrite (NO2), and nitrate (NO3) are all nitrogenous (nitrogen containing) wastes. All living aquarium animals whether they be fish or invertebrates excrete these wastes, and they are also produced by the decay of protein-containing organic matter (uneaten food, detritus, dead fish or inverts, etc.). The nitrogen cycle breaks down these wastes in a series of steps into nitrogen gas (N2) which leaves the aquarium as bubbles.

The nitrogen cycle begins with ammonia, which is highly poisonous. In the first step of the cycle, Nitrosomonas bacteria reduce ammonia to nitrite, which is also very toxic, but slightly less so. In the second step of the nitrogen cycle, Nitrobacter bacteria convert the nitrite to nitrate, which is relatively harmless but can become harmful when it accumulates in high enough levels. In the third and final step of the cycle, denitrifying bacteria then convert the nitrate into completely harmless N2, which of course bubbles out of the tank as nitrogen gas. In this way, thanks to the nitrogen cycle, dangerous wastes are converted into progressively less harmful compounds and finally removed from the aquarium altogether.

When we set up a new aquarium, and wait for it to cycle, we are simply allowing a big enough population of these different types of bacteria to build up in the biofilter to break down all of the wastes that will be produced when the aquarium is stocked. If we don’t wait long enough for the cycle to complete itself and the biofiltration to become fully established, and hastily add too many specimens to a new aquarium too soon, they will die from ammonia poisoning or nitrite toxicity. This is such a common mistake among us impatient aquarists, that when fish get sick and/or die from ammonia/ntrite poisoning, it is commonly called the "new tank syndrome."

When your aquarium has completely cycled, the ammonia levels will stay at zero because, now that your biofilter is fully established, there is a large enough population of aerobic (oxygen loving) nitrifying Nitrosomonas bacteria to reduce all of the ammonia to nitrite as fast as the ammonia is being produced. The nitrite levels will likewise stay at zero because there is also a large enough population of aerobic (oxygen loving) nitrifying Nitrobacter bacteria to convert all of the nitrite to nitrate as fast as the nitrite is being produced.

The nitrate levels ordinarily continue to build up, however, because there are simply not enough anaerobic (oxygen hating) denitrifying bacteria to convert all of the nitrate that’s being produced into nitrogen (N2). Since nitrates are being produced faster than they can be transformed to nitrogen, the excess nitrates accumulate steadily in your aquarium.

That’s perfectly normal, since the denitrifying bacteria that carry out that final step, the conversion of nitrate (NO3) to nitrogen (N2), are anaerobes that can only exist in the absence of oxygen. For our aquariums to support life, and for the fish and invertebrates to breathe and survive, our tanks must be well aerated and well circulated so that there’s plenty of dissolved oxygen in the water at all times. That means there are normally very few areas in our aquariums where anaerobic denitrifying bacteria can survive, limiting their population accordingly (which is generally good, since some anaerobes produce deadly hydrogen sulfide gas during the decay of organic matter and would poison our tanks if allowed to proliferate).

Consequently, most aquariums lack a sufficient population of anaerobic denitrifying bacteria to complete the nitrogen cycle and convert nitrate to nitrogen as fast as the nitrates are being produced. The only way to keep the nitrates from building up to harmful levels in such setups is with regular water changes and by harvesting Caulerpa or other macroalgae periodically after it has utilized nitrates for growth. Overcrowding, overfeeding, or under filtration exacerbate the problem by resulting in more nitrates being produced and more frequent water changes being required to control the nitrate levels.

Live rock helps because the oxygen-poor interior of the rock allows anaerobic denitrifying bacteria to grow and break down nitrates. A deep live sand bed (DLSB) also helps because anaerobic denitrifying bacteria can flourish and break down nitrates at a certain depth below the sand where oxygenated water no longer penetrates, but a DLSB can sometimes be difficult to set up and manage properly if you’re inexperienced with live sand. Both live rock and deep live sand beds give aquaria denitrification ability — the ability to complete the cycle and convert nitrate to harmless nitrogen. Ordinarily, about 1-2 pounds of live rock per gallon is recommended – that amount of LR will provide your aquarium with all of the biofiltration you need, as well as adequate denitrification ability. You will then keep nitrates at harmless levels by performing regular water changes, harvesting Caulerpa macroalgae periodically, and good aquarium management.

So nitrate is simply the end product of the process of nitrification, formed during the Nitrogen Cycle by the oxidation of nitrite by aerobic bacteria. Nitrates always tend to build up in a system over time, sometimes in sneaky ways you wouldn’t expect. For example, here is an article from Thiel Aqua Tech that discusses some of the hidden ways nitrate can enter your system:

Click here: No nitrate, removal nitrate, denitrating, denitration
<<http://www.athiel.com/lib/nonitrate1.html>&gt;

One of the sneaky or hidden ways phosphates, nitrates, silicates and other undesirable compounds can enter our aquariums is through the tap water reuse for water changes or topping off our tanks. If the water quality in your town is not what it should be, you may want to consider buying reverse osmosis/deinonized water (RO/DI) for your water changes. Most well-stocked pet shops that handle marine fish sell RO/DI water as a service for their customers for between 25 and 50 cents a gallon. If your LFS does not, WalMart sell RO/DI water by the gallon for around 60 cents, and you should be able to find a Wal-Mart nearby.

Natural seawater is another good option for water changes. Like RO/DI water, natural seawater can be purchased at fish stores for around $1.00 a gallon, depending on where you live. It sounds expensive, but when you consider the alternative — paying for artificial salt mix and RO/DI water and mixing your own saltwater — then natural seawater is not a bad bargain at all. It has unsurpassed water quality and seahorses thrive in it.

You should also be aware that freshly mixed saltwater can have residual levels of ammonia, but if you aerate the newly mixed saltwater for 24-48 before you perform the water changes, the ammonia will be dissipated.

Good ways to reduce nitrates in your aquarium include adding more live rock, installing a deep live sand bed (preferably in a sump), installing a protein skimmer on your tank if your not already using one, and growing and harvesting fast-growing macroalgae such as Caulerpa.

Protein skimmers help reduce nitrates by removing dissolved organics from the water before they can enter the nitrogen cycle. The majority of the undesirable metabolites, organic wastes and excess nutrients that accumulate in our aquariums and degrade water quality are "surface-active," meaning they are attracted to and collect near the surface of a gas-liquid interface. Skimmers take advantage of this fact by using a column of very fine air bubbles mixed with aquarium water to trap dissolved organics and remove them from our systems. This air-water mixture is lighter than the surrounding aquarium and rises up the column of the skimmer until the foam eventually spills into a special collection cup atop the skimmer, which can be removed and emptied as needed. Proteins and other organic molecules, waste products, uneaten food and excess nutrients, and a host of other undesirable compounds stick to the surface of the bubbles and are carried away along with the foam and removed from the aquarium. As a result of this process, these purification devices are typically known as foam separators, foam fractionators, air-strippers, or simply protein skimmers.

In my experience, nothing improves water quality like a good protein skimmer. They provides many benefits for a seahorse setup, including efficient nutrient export, reducing the effective bioload, and increasing both the Redox potential and dissolved oxygen levels in the water. They do a tremendous job of removing excess organics from the aquarium, including phenols, albumin, dissolved organic acids, and chromophoric (color causing) compounds. Their ability to remove dissolved wastes BEFORE they have a chance to break down and degrade water quality makes them indispensable for controlling nuisance algae. A good protein skimmer is an invaluable piece of equipment for keeping your nitrates low and your water quality high when feeding a whole herd of these sloppy eaters in a closed-system aquarium.

I also like the use of macroalgaes for controlling nitrate and nuisance algae. Macroalgae use nitrate for growth just like plant fertilizer and pruning the macros regularly is a good way to export nitrate from your system. However, if the macros die in your system, they’ll release the nitrate they’ve consumed back into the aquarium. Fast-growing Caulerpa needs to be thinned out regularly to prevent vegetative events and avoid this from happening, as discussed below:

Macroalgae act as an excellent form of natural filtration, reducing the available levels of phosphates and nitrites/nitrates. Be sure to thin out the fast-growing Caulerpa regularly; when you remove the clippings, you’re exporting phosphates, nitrates and other nutrients from the tank, thereby helping to maintain good water quality, and periodically harvesting the runners helps keep it from going sexual.

When thinning out or harvesting macroalgae, take care not to actually cut it. Remember, you’re not pruning hedges or trimming trees — the idea is to carefully pull up and remove continuous, unbroken fronds. Simply thin out the colony of excess strands, gently plucking up convenient fronds that can be readily removed intact. A little breakage is fine, but cutting or breaking too many strands will result in leaching undesirable substances into the aquarium water as the Caulerpa’s lifeblood drains away. Too much cutting or breaking can thus sap the colony’s strength and cause die offs or trigger the dreaded vegetative events that judicious pruning otherwise prevents.

Another product I like for removing excess ammonia, nitrite, and nitrate is the Poly-Filter Pad (by Poly-Bio-Marine) Here is a product review on Poly Filters that touches on some good ways to use them:

Click here: Saltwater Aquariums Product Review – Poly-Bio-Marine Inc. – Poly Filter Pad
<<http://saltaquarium.about.com/cs/filtration/l/blprbiomarinpad>&gt;

Speaking of chemical additives, if you use activated carbon in your tank, it’s also very important to make sure that your carbon is phosphate free and that you change it religiously, replacing the old carbon with fresh new carbon every six weeks or so. (If you don’t replace the activated carbon regularly, it could eventually began to leach the wastes and organic compounds it has absorbed back into the aquarium water once it reaches its capacity.) Carbon is activated two ways, either with steam or with phosphoric acid. The type of carbon that is activated with phosphoric acid contains phosphates, which can likewise be leached back into the aquarium water and promote the growth of nuisance algae. So you will want to avoid that type of activated carbon, particularly when you’re having a problem with nuisance algae. The carton or box that the activated carbon came in will be clearly labeled that it is "steam activated" or "phosphate free" or something to that effect if it’s a suitable brand for your aquarium. Activated carbon that is low ash and phosphate-free can help control an outbreak of hair algae if it is changed and replaced with fresh carbon diligently; however, activated carbon that is not free of phosphates or that is not changed regularly can actually contribute to a problem with nuisance algae and degrade your water quality.

Finally, commercially made denitrators (special filters housing a large population of anaerobic denitrifying bacteria) are also available. They do a tremendous job of controlling nitrates but are rather expensive and tend to be high maintenance, often requiring regular "feeding" and carefully controlled flow rates to operate properly.

In summary, some of the measures that will help control nitrates and phosphates (and excess nutrients in general) in the aquarium are the following:

1) Make sure your protein skimmer is working correctly. A protein skimmer works 24 hours a day to remove excess waste and nutrients from a tank. If the venturi is clogged on a venturi skimmer or there is another problem with other skimmer designs, waste will not be exported from your tank and algae will take advantage of the waste.

2) Perform regular water changes. Regular water changes will decrease the level of wastes and nutrients in the water. But the water changes won’t do much good if your tap water itself contains phosphates and amines. Depending on how high the nitrate levels become, increasingthe proportion of water that you change each time may be necessary to help reduce those nitrates. There is an article about nitrate reduction at <<http://www.about.com/>&gt; in the saltwater section that really explains water changes (gives you the math), on actually how little you are reducing nitrates with small water changes when you have high nitrates.

3) Make sure makeup water is pure. Phosphates and nitrates often found in tap water. Phosphate and nitrate test kits will show if your tap water is contributing to your algae problem. If phosphate and nitrate levels are more than 0 ppm (some tap water measures out at over 50 ppm nitrate), filter the water through a RO/DI unit before using it as makeup freshwater or as source water for saltwater changes, or purchase RO water from a vendor.

4) Add additional detritivores to your cleanup crew. If excess food isn’t eaten, it will decay and add to the nutrients and waste in the tank. More microhermit crabs, Nassarius snails and cleaner shrimp will help ferret out any uneaten Mysis before it breaks down and enters the nitrogen cycle to eventually end up as excess nitrate.

5) Introduce macroalgae to consume excess nutrients and nitrates. If regular pruning is done, fast-growing Caulerpa will maintain its color and high growth rates without going sexual. Better yet, an algal filter or "algae scrubber" can be established in a sump or refugium.

6) Chemical controls. Phosphate absorbers can remove excess phosphates just as nitrate sponges will do with nitrates, and Poly Filter pads can also help absorb excess nitrates, changing color as they do so, which helps indicate when the Poly Filter needs to be changed. Low ash activated carbon that is free of phosphates will also help remove such nutrients if it is change religiously and replaced with new carbon.

7) Controlled addition of food to tank. Don’t broadcast feed, scattering Mysis throughout the tank. Instead, target feed your seahorses or use a feeding station. Don’t overfeed, cleanup leftovers promptly, and observe fast days religiously.

8) Add additional live rock and/or a DLSB (preferably in a sump). Both live rock and a deep live sand bed can carry out denitrification and convert nitrate into harmless nitrogen gas, which eventually bubbles out of the aquarium.

When live rock is going to be serving as the primary means of biological filtration for an aquarium, I recommend using up to 1-2 pounds of live rock per gallon for that purpose. Since your 49-gallon aquarium has considerably less live rock than that, you might consider adding another 10-20 pounds of choice live rock to beef up the denitrification ability in your tank and help control the nitrate as even better.

Best of luck getting your nitrate levels down where you want them to be, Sean. I would say that as soon as you’re nitrite levels in the main tank are back down to zero, you can go ahead and transfer your new Mustangs back to the main tank again. I think they will do better in the main tank even if the nitrate levels are somewhat elevated than they would do in a 10-gallon quarantine tank over an extended period.

Respectfully,
Pete Giwojna

Dear Sean:

Thanks for the update! You did a terrific job of reducing your nitrates and a level of 5 ppm is excellent. It’s good to hear that your seahorses appreciate the new lighting system you have installed and have rewarded you by displaying a healthy interest in courtship and breeding.

It’s a good idea to line up live food sources in advance whenever you are expecting young, and that’s a fine plan to try both the easy rearing method and the more complicated live food chain technique for rearing (establishing phytoplankton cultures that are then used to raise copepods and/or rotifers) and see which one produces the best results for you. I would be happy to outline one method for culturing the microalgae (phytoplankton) and rotifers and copepods (zooplankton) for you below, and then I’ll refer you to some other sources of good information on the subject, sir.

Copepods at the right stage of development are the most nutritious food that seahorse fry can eat. Marine copepods are the ideal food for rearing seahorses fry. They are a natural prey item that constitutes a large portion of the diet of fish larvae in the ocean, and many marine fishes have evolved efficient feeding strategies for preying on them as their primary foods. This includes seahorses, whose tubular snouts are adapted specifically for feeding on tiny crustaceans such as ‘pods, and which have developed a sedentary lifestyle as ambush predators that allows them to capture them with maximum efficiency and a minimum expenditure of energy. The tiny size of the copepod nauplii allows even the smallest seahorse fry to eat them, and they are a feed-and-forget food that will survive in the nursery tank until eaten. The distinctive swimming style of copepod nauplii triggers a strong feeding response from seahorse fry, and ‘pods have naturally high levels of essentially fatty acids. They are superior to rotifers in all these respects (seahorse fry often reject rotifers because they don’t move in the "right" way and simply don’t trigger their feeding instincts) and I recommend that aquarists who are raising pelagic fry concentrate on culturing copepods.

Seahorse fry alter their diet as they grow (Vincent, 1990). This may be due to the fact that they change microhabits as they develop (e.g., when pelagic fry complete their planktonic stage and begin to feed at the bottom as they begin orienting to the substrate). Or it may simply be due to the fact that they become better hunters and perfect their feeding skills as they grow, thus enabling them to tackle larger, more active prey (Vincent, 1990). Whatever the cause, one good way to keep up with the fry’s changing dietary requirements is by providing them with cultured copepods at progressively later stages of development. The first step in culturing rotifers or copepods is to establish a good culture of marine microalgae or phytoplankton.

Step 1: Providing Marine Microalgae (Phytoplankton).

Marine microalgae or phytoplankton is available from many sources. It can be cultured at home, and if you have a green thumb and are experienced with such greenwater cultures, that may be your best option. However, home culturing may not be for everyone. Greenwater cultures can be tricky to maintain. They are easily contaminated and are prone to "crashing" suddenly and unpredictably, which can have dire consequences if you are relying on the phytoplankton to provide food for your seahorse fry.

Alas, I am one of those unfortunates who cannot seem to maintain a decent greenwater culture for any length of time no matter what I try. Consequently, I now much prefer to obtain live marine phytoplankton from other sources rather than attempting to culture my own. Commercially available phytoplankton tends to be more concentrated than homegrown cultures as a rule, and I find purchasing it to be far more convenient, efficient, and productive. Given my repeated failures and the time I spent for naught on my own greenwater cultures, I’m certain that buying live phytoplankton is more economical for me in the long run as well. If you are inexperienced with greenwater culture or simply lack the time to culture your own, I recommend buying your live phytoplankton instead (see the Resources page for suppliers). Whichever source you decide to use, home grown or store bought, make sure you use it strictly according to instructions to prevent contamination and spoilage of the phytoplankton.

The type of phytoplankton or microalgae you use is not that crucial. Chlorella is one of the most popular microalgae used in mariculture (Wilkerson, 1995), but Dunaliella also works extremely well and is recommended by Dr. Amanda Vincent (Vincent, 1995c), an authority on the breeding habits of seahorses. Serious breeders often use a mixture of different types of phytoplankton to feed copepods or rotifers, rather than a microalgae monoculture, with the goal of enhancing the nutritional profile of the ‘pods or rotis as much as possible (David Warland, pers. com.).

There is a great deal of merit to that approach, but in the past, maintaining separate cultures of different species of microalgae was beyond the capabilities of most home hobbyists, myself included. I prefer to keep things simple and I have always used Nannochlroposis as the phytoplankton I feed to copepods, both because it produces good results and because it is commercially available from a number of sources. To simplify things all the further, I purchase my Nannochlroposis in quantity as needed, rather than struggling with phytoplankton cultures.

The product I like best at the moment for this now includes a concentrated mixture of live marine phytoplankton (two species of Nannochlroposis, N. oculata and N. salina, as well as a Chlorella sp.) in every bottle (DT’s Live Marine Phytoplankton, 2003). That makes it a simple matter to provide my ‘pods with a diversified diet to maximize their nutritional value as fry food — I just unscrew the cap on the bottle and pour the requisite amount of this phytoplankton mixture into my culture tank whenever it’s losing its greenish tinge, and I’m in business (DT’s Live Marine Phytoplankton, 2003)! No muss, no fuss. Quick, easy and effective — just the way I like it!

Step 2: Culturing Zooplankton (copepods and/or rotifers).

We will be using standard 10-gallon glass aquaria as our batch culture tanks. It’s a good idea to run at least 2 such tanks simultaneously; that way, if one of the cultures falters, the other tank can pick up the slack and you won’t miss a beat. Depending on how many seahorse fry you are rearing, you many need to operate several such tanks to assure you will be producing sufficient food for them all.

Fill each of these culture tanks slightly less than half full with synthetic saltwater, adjust the salinity of the culture tank to match the salinity of your nursery tanks, and maintain the pH at 7.9 or below (Rhodes, 2003). This will assure that the copepods (or rotifers) we are culturing do not experience any salinity shock when we feed them to our seahorse fry. No heater is necessary — the cultures will do just fine at room temperature (24C-28C is optimum). Provide very low aeration (Rhodes, 2003). Airstones are unnecessary — a naked bubbler stem is sufficient. Adjust the airflow so it produces a slow, steady stream of coarse air bubbles (slow enough so that you can count the individual bubbles). Ambient room lighting is adequate or you may provide low wattage fluorescent lighting if you prefer.

Add enough greenwater (either commercially produced phytoplankton you’ve purchased or your own homegrown microalgae) to tinge the culture tanks green, and you’re ready to start culturing copepods. All that remains at this point is to "seed" the culture tanks with copepods. Add a starter culture of marine copepods to each tank, acclimating the ‘pods if necessary exactly as you would acclimate a new aquarium fish. They will do the rest.

To nurture the copepods, simply maintain a nice green tint to the culture water by adding more phytoplankton whenever the water in the tanks begins to clear in color. (Be conservative with these phyto-feedings. One dose of phytoplankton every 7-10 days is generally adequate, depending on production and your copepod harvest rates; Rhodes, 2003.) The ‘pod population in the culture tanks will double every 2-3 days, depending on the temperature and how well they are fed (Rhodes, 2003), and as soon as the population builds up sufficiently, we can begin to harvest copepods to feed to our seahorse fry. When you begin to notice numbers of copepods gathering on the tank glass, that’s a good indication that their population density can support daily harvesting.

The best way to harvest copepod nauplii is to strain the desired amount from the culture tank using a 35-micron sieve and then rinse or backwash the strainer in the nursery tank (Rhodes, 2003). Alternate which culture tank you harvest the copepods from for each feeding in order to avoid depleting the ‘pod population too much in any given tank.

Periodically, it will be necessary to restart the copepod culture tanks to filter out the detritus that accumulates on the bottom. This is typically done every month or two (Rhodes, 2003) and is a surprisingly simple process. Just siphon out the water from the culture tank, straining the water in the process in order to retain the copepods. A 125 -micron sieve works well for a strainer. That size mesh will retain all the reproductive adults you need to restart your culture (Rhodes, 2003). It’s a good idea to use a small diameter siphon at first, being careful to suck up as little of the detritus as possible since it will clog up your strainer and your goal at this point is to recover as many copepods as you can. Once you’ve strained out most of the ‘pods, backwash them into container of clean saltwater and set them aside to seed the culture tank after you’ve finished cleaning it. Having saved as many pods as possible, switch to a larger siphon and drain the culture tank completely, removing all of the accumulated detritus. Fill the tank half way with freshly mixed saltwater you’ve prepared in advance and adjust the aeration. Then return the copepods you strained out previously and add enough concentrated phytoplankton to tinge the water green, and your culture is ready to begin producing again. If you restart your culture tanks on alternate months, one or more of them will be in full production at all times, and you can keep a thriving copepod population going indefinitely in this manner.

If you so desire, rotifers can be cultured in exactly the same manner. The only difference is that the 10-gallon culture tanks should each be seeded with a quart of live rotifers initially (Giwojna, Jan. 1997). When necessary, add enough concentrated phytoplankton or greenwater to keep the rotifer culture tanks slightly green. As long as the rotifers are being fed algae, about 25% of the rotifer cultures can be harvested each day to feed to your seahorse fry (Wilkerson, 1995). Try to keep more than one rotifer culture going at all times in case of crashes, and be sure to keep the bottom of the culture tanks scrupulously clean (Giwojna, Jan. 1997).

In fact, you can even maintain a dual culture of copepods and rotifers in the same tank if you wish. But you must avoid cross-contamination of your culture tanks with brine shrimp at all costs! Newly hatched brine shrimp (Artemia nauplii) are considerably larger than either copepods or rotifers, and the Artemia will happily fed on them as well as the phytoplankton. So if any brine shrimp ever find their way into your culture tanks, you will very shortly thereafter be culturing Artemia instead of ‘pods or rotis, leaving you with nothing but live food that’s too large for pelagic fry to eat.

Harpacticoid copepods such as Nitokra lacustris go through 6 naupliar stages as they grow, followed by 6 copepodite stages, before they become reproductive adults. They range in size from 45 microns (smaller than rotifers) up to 270 microns as full-sized adults. The many different stages of development copepods undergo is actually a blessing for the aquarist since it makes it possible to provide progressively larger ‘pods to the seahorse fry as they grow simply by using sieves with different sized mesh to harvest them. For instance, a 35-micron sieve will gather up even the smallest copepod nauplii for newborn fry, while a 125-micron will collect only adult-sized pods for older fry and juveniles, leaving the smaller ‘pods behind to develop further. An 80-micron sieve will take intermediate-size ‘pods along with the adults.

Whether you’re culturing rotifers or copepod nauplii, pelagic seahorse fry should be fed continuously starting 6-12 hours after birth (Giwojna, Jan. 1997). Dr. Amanda Vincent recommends feeding 2 plankton nets of rotifers (or ‘pods) 5-7 times daily or whenever no plankton is visible in the nursery tanks (Vincent, 1995c). In addition, she keeps a drip of diluted plankton (i.e., rotifers or copepods) going at the rate of 10 liters/day at all times (Giwojna, Jan. 1997). (A bucket of copepod-laden or rotifer-rich saltwater set on top of the nursery tank will suffice for this–just use a length of airline tubing as a siphon and adjust the drip rate with a valve; Vincent, 1995c.)

Okay, Sean, that’s the quick rundown on culturing phytoplankton in order to raise the zooplankton (i.e., copepods and/or rotifers) for your seahorse fry. for more information on these culture techniques, please refer to the Plankton Culture Manual published by Florida Aqua Farms.

In addition, I highly recommend Joyce Wilkerson’s excellent article called ”Captive Food Chain,” which appeared in the Fall issue of The Breeder’s Registry (Volume 3, Number 4: 1-4.) It describes a larval rearing system that would be ideal for raising seahorses, including step-by-step instructions for culturing microalgae, rotifers, and Artemia. (The Breeder’s Registry is a central depository of information on propagating marine life. Its objectives are to encourage closed-system captive breeding of marine organisms in order to limit demands on wild populations, and to act as a registry for active breeders to acquire and exchange broodstock and increase gene pools.)

To obtain a copy of Joyce Wilkerson’s ”Captive Food Chain” article or to request information on breeding and rearing seahorses in general, contact Stanley D. Brown at:
The Breeder’s Registry, P.O. Box 255373, Sacramento, California 95865-5373
Telephone: (916) 487-3752 E-mail address: [email protected]

And don’t forget to check out The Breeder’s Registry’s online articles about rearing at the following site:

http://www.breedersregistry.org/Articles/index.htm

Best of luck with your new seahorses, Sean! Here’s hoping they produce a brood of healthy young for you in the near future.

Happy Trails!
Pete Giwojna