Dear Sue:

Pete Giwojna

Dear Sue:


I’m sorry to hear about the outbreak of nuisance algae that is detracting from the appearance of the tank, and it is a good idea for you to try to create additional flow that won’t be too overwhelming for the seahorses in order to help get the cyano outbreak under control. Most of the time the brown algae (diatoms) will disappear on its own as suddenly as it appeared after it has consume the available amount of silicates in the aquarium, so the diatoms should run their course and then go away. The cyanobacteria (red slime algae) will be the bigger problem in the long term.


Can you tell me what your basic water quality parameters (pH, water temperature, specific gravity or salinity, and the levels of ammonia, nitrite, and nitrate) are at this time, Sue?  In particular, I would like to know what the current readings for nitrates and phosphates are, since excess amounts of nitrate and/or phosphate are often associated with outbreaks of nuisance algae. There are some easy ways to eliminate the excess nitrate and phosphate, if that’s the case, and that would be an important step to eliminating the red slime algae that is overgrowing your aquarium.


For instance, there could be a lot of organic loading and organic carbon building up in the tank that could be fueling the growth of the Cyanobacteria. As you know, Sue, when nuisance algae gets out of control, it’s often an indication of excess nutrient loading and declining water quality, and an outbreak of hair algae or Cyanobacteria (red slime algae) is very often associated with undercirculation and low pH and/or alkalinity problems in the aquarium. It is common for a newly established aquarium to experience a bloom of diatoms or to go through a phase in the algae succession cycle where nuisance algae gains a toehold in the tank, but an aquarium that has been overgrown with slime algae or hair algae is not a healthy system and very likely has water quality issues that need to be corrected.  It may be worth checking the total alkalinity or carbonate hardness in your tank as a precaution in order to see if they are running on the low side.

Hair algae and slime algae can be most unsightly but they are not directly harmful to seahorses. They are, however, an indicator of poor water quality since they thrive on excess nutrients in the aquarium (especially phosphates and nitrates), and of course marginal water quality can certainly be detrimental to our seahorses in the long term. And, as you know, if you don’t nip a problem with nuisance algae in the bud, it can take over your entire aquarium and ruin it.

The appearance of nuisance algae in your aquarium most likely indicates that nitrates and phosphates are building up in the tank, but it may also indicate that your aquarium bulbs need to be replaced. As they age, the spectrum of light put out by aquarium lamps changes, shifting more towards the red end of the spectrum, which favors the growth of hair algae and slime algae rather than coralline algae or macroalgae. So you might consider replacing your aquarium bulbs with new ones at this time, Sue, if it has been several months since you last replaced them.

Here are some other suggestions for controlling phosphates and nitrates and getting nuisance algae under control. I realize that many of them may not apply to your case, Sue, but please read through all of them carefully anyway because they may give you a much better idea of why nuisance algae gets started in an aquarium and how to get rid of it once and for all.

The best way to get rid of red slime algae and hair algae for good is to eliminate the excess nutrients that fuel its growth. There are a number of chemical filtration media products that will absorb phosphates from the water; any good LFS that has reef tanks and carries marine fish and invertebrates should have a number of such products from which to choose.

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 couple of weeks or so. (If you don’t replace the activated carbon regularly, there is a chance that it may begin 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 nuisance algae if it is changed or 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.

In and of themselves, nitrates are relatively harmless and midrange levels are nothing to be too alarmed about. Ideally, though, we’d like to keep them under 10 ppm, if possible, and you will see adverse effects on the health of your seahorses in the long run if the nitrates exceed 20 ppm. So if your nitrates are running on the high side and you have a problem with nuisance algae, you need to try to reduce them as much as possible. 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) and heterotrophic 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 often 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 methane and/or hydrogen sulfide gas during the decay of organic matter and would poison our tanks if allowed to proliferate in unsuitable areas of the tank).

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

One of the sneaky or hidden ways phosphates, nitrates, silicates and other undesirable compounds can enter our aquariums is through the tap water we use 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 a 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 in your sump, installing a protein skimmer on your tank if you are not already using one, and growing and harvesting fast-growing macroalgae such as Gracilaria and Botryocladia (red grape Caulerpa) in the main tank or Chaetomorpha spaghetti algae and Caulerpa in a well-planted sump or refugium.


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 macroalgae 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 pruned properly 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 prune and trim back 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 pruning the runners helps keep it from going sexual.


When pruning or trimming back 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 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



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


The hobbyist should also be aware that dead spots and low flow areas, as well as low pH levels, favor the growth of nuisance algae rather than coralline or macroalgae and marine plants.  Eliminating dead spots and stabilizing your pH at 8.0-8.2 can therefore help tip the balance back in the favor of macros and coralline algae, and help prevent problems with nuisance algae.


One simple measure that can thus make a big difference is to try positioning one or more small powerheads so that they increase the circulation in the area where the nuisance algae tends to grow.  Better water movement and higher oxygen levels will naturally tend to minimize the growth of slime algae and hair algae in these problem areas.  Just be sure to shield or screen off the intakes for the powerheads so that a curious seahorse won’t get its tail injured by the impeller.

In summary, some of the measures that will help control nitrates and phosphates (and excess nutrients in general), or otherwise help control nuisance algae 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. In order to function efficiently, the protein skimmer must be cleaned regularly, including inside the cylinder where the bubble column forms to provide the foam fractionation.

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, increasing the proportion of water that you change each time may be necessary to help reduce those nitrates. There is an article about nitrate reduction at <<>&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 are 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, as will the steady accumulation of detritus and mulm in an aquarium. More microhermit crabs, Nassarius snails and cleaner shrimp will help ferret out any uneaten Mysis and clean up detritus before it breaks down and enters the nitrogen cycle to eventually end up as excess nitrate.

So if you’re having a problem with nuisance algae, consider bolstering your cleanup crew with additional snails and/or micro-hermit crabs that eat slime algae and other types of nuisance algae. Astrea snails, red foot moon snails, and Scarlet reef hermit crabs (Paguristes cadenati) all fit the bill and would be good additions in that regard.

Under the circumstances, Sue, the first thing that I would suggest trying is biological control in the form of additional aquarium janitors that have a special fondness for Cyanobacteria.  I recommend augmenting the cleanup crew for your seahorse tank with scavengers that specifically like to feed on the cyanobacteria or red slime algae, Sue. Especially good for this are the Banded Trochus Snails and Tiger Sand Conchs that are available from Aquacon ( and the Mexican Red Leg Hermit Crabs (Clibanarius digueti) and certain Cerith snails (i.e., Cerithium strercusmuscarum), which you can get from GARF at the following website (just copy the following URL and paste it in your Web browser and then press “Enter,” Sue — that will take you directly to the right site):


They cost just a few dollars apiece and I would recommend getting one Tiger Sand Conch plus a good half-dozen Banded Trochus Snails and at perhaps five of the Mexican Red Leg Hermits plus a handful of the Cerithium strercusmuscarum snails, depending on how severe the problem with the slime algae has become. (However, you should not need any of the Live Sand Activator.)

So it would make good sense to bolster your cleanup crew with additional snails and/or micro-hermit crabs that eat red slime algae. Astrea snails, red foot moon snails, and Scarlet reef hermit crabs (Paguristes cadenati) or other seahorse-safe scavengers that all fit the bill and would be good additions in that regard.

Introduced as soon as possible to a new aquarium, as soon as the ammonia and nitrite levels are safe, Astrea snails effectively limit the development of all microalgae. In other words, they are good at eating diatoms, but will consume red slime and green hair algae as well. The Scarlet Reef Hermit Crab (Paguristes cadenati) is a colorful micro-hermit that’s a harmless herbivore. So cannibalism isn’t a concern at all for these fellows, nor are they likely to develop a taste for escargot. As hermits go, most of the time the Scarlet Reefs are perfect little gentleman and attractive to boot. I even use them in my dwarf seahorse tanks. Best of all, they eat all kinds of algae, including nuisance algae such as red, green and brown slimes, as well as green hair algae.


And, as we’ve already discussed, Mexican Red Leg Hermit Crabs (Clibanarius digueti) and certain Cerith snails really like to eat cyanobacteria or red slime algae. Garf ( offers a Reef Janitors package with hermits (chibanarius or clibanarious digueti, mexican dwarf hermit) and the snail (Cerithium strercusmuscarum), which are said to do an excellent job of cleaning up red slime algae.

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, and Poly Filter pads can 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. Thoroughly rinse your frozen Mysis before enriching it, since these shrimp juices that accumulate when the Mysis thaws can be rocket fuel for nuisance algae.


It is especially important for seahorse keepers to rinse the excess shrimp juice from the frozen Mysis you prepare before you feed it to the seahorses, and as long as it’s just a quick rinse then it really doesn’t matter if it’s RO water or saltwater from the tank or even ordinary tap water that you use to gently rinse it. But that could rinse of the thawed frozen Mysis can pay big benefits for the home hobbyist by removing excess shrimp juice before the Mysis is fed to the seahorses because those shrimp juices are like rocket fuel for nuisance algae, stimulating rapid growth of hair algae or cyanobacteria (red slime algae).

8) Eliminate dead spots and increase the water flow in areas where the nuisance algae tends to grow.

9) Maintain the pH in total alkalinity of the aquarium in the proper range. Monitor alkalinity or carbonate hardness and the calcium levels in the tank as well as the pH.

10) Replace your aquarium lamps regularly to assure that the spectrum of light they put out favors the growth of coralline algae and macroalgae. (Over time, as bulbs age, they begin to put out light shifted more towards the red-end of the spectrum, which encourages the growth of hair algae.)

11) Reduce the photoperiod in your aquarium is much as possible to cut down on the light that’s available for photosynthesis.

12) Increase the circulation in the aquarium to eliminate dead spots, particularly in the areas where the hair algae tends to grow.

13) Physically remove as much of the nuisance algae as possible. Some aquarists go as far as to remove all of the live rock from the aquarium and painstakingly scrub it free of the hair algae or even boil it to rid it of the nuisance algae, but boiling it also destroys the beneficial nitrifying and denitrifying bacteria it houses.


Okay, Sue, those are some additional suggestions to keep in mind whenever you are dealing with an outbreak of nuisance algae. I know that you are probably already well aware of most of the suggestions and that very few of them apply to your seahorse tank, but they may give you an idea or two that can help.


In particular, I would also suggest that you obtain some Natural Nitrate Reducer from Instant Ocean to further reduce your nitrate levels, if necessary, Sue. It can get your nitrate level down to zero within 3-4 weeks when used properly and it is not a chemical method of removing nitrates at all. Rather, it is a mixture of special enzymes and polymers that facilitate the breakdown of nitrate biologically.


Here is some additional information about this product you may find helpful:


Natural Nitrate Reducer by Instant Ocean (miracle product for reducing nitrates)

Principal Ingredients: Patented Suspended Biodegradable Polymers

*Promotes Natural Biological Process

*Reduces Unwanted Nutrients

*Increases Buffering Capacity

*Time-Release Action


Instant Ocean’s patented formula promotes the natural denitrification process of converting nitrate to nitrogen gas. This advanced biochemistry is found in nature and helps maintain healthy aquarium conditions.


Directions for Use:


shake well before using. Use 10 mL per every 10 gallons. For easy dosing, use the top of the screw cap, fill in or ring for 5 mm and top of cap for 10 mL.




Dose rate can be doubled per week for additional nitrate control. Depending on the study concentration of nitrate in the aquarium, it can take a few weeks to reach desired levels. Once achieved, levels will remain low.


In your case, Sue, with a very moderate level of nitrates (10 ppm) it should not be necessary to double the dose rate and administer the Natural Nitrate Reducer twice a week; adding it to the aquarium water once a week should suffice for your tank. But for nitrate levels > 20 ppm, don’t hesitate to add Natural Nitrate Reducer twice a week.

For more information, check out the following online articles which are loaded with additional tips and suggestions for controlling outbreaks of nuisance algae. Please read these carefully, since they’ll give you many more good ideas for combating your problem with hair algae:



Click here: GreenAlgContFAQs

Click here: – Articles – Reeftank Maintenance – Algae Control FAQ

If the tap water or well water in your area is of dubious quality, and you don’t mind lugging containers of water home from the pet store, then purchasing pre-mixed saltwater from your local fish store is often a good option. Many seahorse keepers purchase reverse osmosis/deinonized water (RO/DI) for their 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. For example, WalMart sell RO/DI water by the gallon for around 60 cents.

Natural seawater is another good option for a seahorse setup. Like RO/DI water, natural seawater can often 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.


There are some good products available that will eliminate red slime algae chemically, simply by adding the proper amount to your aquarium water, Sue, but unless you address the underlying causes, as we have discussed above, it will very likely come back worse than ever within a few weeks, so I recommend that you avoid the temptation to eliminate the red slime algae (cyanobacteria) by using chemical means.


Most of the products that are available for controlling red slime algae chemically, such as Chemi-Clean, use an antibiotic of some sort as their active ingredient, Sue, because the slime algae is actually a type of bacteria (Cyanobacteria). Chemi-Clean can help to control red slime algae, but often does not eliminated from the aquarium once and for all. The Chemi-Clean seems to do a very good job of eradicating the red slime algae the first time you use it, but it is only treating the symptoms of the problem and not the cause, so very often the red slime algae reappears after a few weeks.


You can try the Chemi-Clean again, but the second time you use the product it may not work as well, and when the red slime algae eventually reappears, you will no longer be able to control it using the Chemi-Clean again. That’s because red slime algae is actually a bacterium (Cyanobacteria), which can develop resistance to the Chemi-Clean when it is used repeatedly.


So, I would suggest that rather relying on any sort of chemicals to try to control the red slime algae, Sue, that you beef up your cleanup crew with scavengers that are especially good at eating red slime algae instead. If you had enough of the proper type of scavengers, they will be able to completely control the red slime algae biologically from now on with a little luck and you won’t have to try to control it chemically anymore.


Best of luck on bolstering your cleanup crew with red slime eating scavengers and eliminating the cyanobacteria from your seahorse tanks, Sue.



Pete Giwojna, Ocean Rider Tech Support

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