Reply To: Film over Kuda’s – Disease?

Pete Giwojna

Dear Red:

I am sorry to hear about the problem that your Hippocampus kuda have developed, sir.

I was unable to access the link for the photos you provided, which only yielded an error message stating “Invalid Dynamic Link,” so I don’t have a good idea as to what this thick slime coat may actually be.

But my first guess would be that it may be some sort of a body fungus, and I would suggest that you copy the following URL, paste it in your web browser, and then press the enter key, which will take you to the following online article:


You’ll find a discussion of possible causes and recommended treatments for marine fungus in the article above.

You might consider a brief dip for the affected seahorses in a concentrated solution of Kordon methylene blue, as described below:

For a quick 10 second dip to treat external fungus, use the following instructions:

For use as a dip for treatment of fungus or external parasitic protozoans and cyanide poisoning:
(a) Prepare a nonmetallic container of sufficient size to contain the fish to be treated by adding water similar to the original aquarium.
(b) Add 5 teaspoons (24.65 ml) per 3 gallons of water. This produces a concentration of 50 ppm. It is not recommended that the concentration be increased beyond 50 ppm.
(c) Place fishes to be treated in this solution for no longer than 10 seconds.
(d) Return fish to original aquarium.

In other words, for a 10-second dip, you’ll want to use 5 teaspoons of the Kordon 3 methylene blue for 3 gallons of water. Time the dip very closely, Marci, and be sure to hold the seahorse in your hand so that he can be removed immediately and return to the main tank after the 10 seconds have elapsed. (Wear disposable plastic gloves, since the concentrated methylene blue will stain your hand a brilliant royal blue for some days or weeks to come otherwise.)

Don’t add the methylene blue to your main tank, as it will destroy nitrifying bacteria.

If you’re going to use the less concentrated dose of methylene blue in order to treat external fungus, Red, then it will require much longer exposure to be effective, and is therefore best administered in a hospital tank for a period of 3-5 days:

Prevention or treatment of fungus or external parasitic protozoans:
(a) Remove carbon filter and continue to operate with mechanical filter media throughout the treatment period.
(b) Add 1 teaspoon of 2.303% Methylene Blue per 10 gallons of water. This produces a concentration of 3 ppm. Continue the treatment for 3 to 5 days.
(c) Make a water change as noted and replace the filter carbon at the conclusion of the treatment.

As you can see above, Red, at that concentration (1 teaspoon per 10 gallons or 1/2 teaspoon per 5 gallons) the methylene blue needs to be administered continuously for 3 to 5 days in order to be effective. If you want to save your biofilter and sensitive invertebrates, this would need to be done in a hospital tank, and you would likely need to perform daily water changes in order to maintain the water quality, after which you would re-dose with the methylene blue.

If you are going to attend treatment using formalin, remember that it is best to administer the formalin as a short-term bath or a series of dips in a separate treatment tank or hospital tank because formalin can be harmful to invertebrates and may have a detrimental impact on the beneficial nitrifying bacteria that provide biological filtration for the aquarium.

Here are the instructions for administering formalin as a short-term bath, Red:

Recommended dosage of 37% formaldehyde (formalin) from Ann at

FORMALIN Short-Term BATH Dosage and Preparation Instructions
Active Ingredient: 37% Formaldehyde
Indication: external parasites
Brand Names: Formalin, Formalin-MS
1. Do NOT use Formalin that has a white residue at the bottom of the bottle. White residue
indicates the presence of Paraformaldehyde which is very toxic.
2. “Formalin 3” by Kordon contains only 3% Formaldehyde. Dosing instructions will need to be modified if using this product.
• Fill a small tank with aged, aerated, dechlorinated marine water. Match the pH, temperature, and salinity to that of the tank the Seahorse is currently in.
• Add an artificial hitch and 1–2 vigorously bubbling airlines. Formalin reduces dissolved O2 so heavy aeration is required.
• Add 1ml/cc of Formalin per one gallon (3.8 liters) of tank water. Allow several minutes for the Formalin to disperse.
• Place the Seahorse into the dip water for 45–60 minutes unless it is showing signs of an adverse reaction. If the Seahorse cannot tolerate the Formalin dip, immediately move it back to the hospital tank.
• Observe the Seahorse for 24hrs for signs of improvement.

[Note: 1 ml = 1 cc and 20 drops equals 1 ml. Also 1000 ml equals ~ 1 quart.]

And here are the instructions for treating seahorses using Formalin 3 by Kordon, Red:

‹open quote›
Formalin 3 by Kordon is the medication I prefer for these treatments. These are the instructions for treating fish with Formalin 3, the Kordon brand of formalin, which is readily available at most fish stores:


The following procedures are suggested for both freshwater and marine systems, unless otherwise noted. It is important to note that some activated carbons can remove formaldehyde from water, but formaldehyde persists for only a few hours in aquariums and does not accumulate in the water.


Successful treatment of diseases of aquarium fishes relies upon several factors. Firstly, as discussed above (“General Diagnosis of parasitic Diseases of Fishes”), a proper diagnosis of the disease must be made, and this can be one of the most difficult tasks facing an aquarist.
Secondly, the start and duration of a treatment is important. A disease which will usually respond to a given medication may not respond if the treatment is started too late, or if the length of treatment is not long enough.

Lastly, the correct medication at the correct dosage must be used with the proper treatment method. Formalin·3, for instance, will not be effective against systemic (internal) diseases of aquarium fishes because the therapeutic effects of the formaldehyde are restricted to those surfaces of the fishes that contact the treated water.

Water changes are another important factor. Some medications state that water changes are not necessary, but the fact is that water changes are always helpful. Depleted dissolved oxygen levels are replenished, dissolved organics are removed as are free-living disease organisms.

Treatment in a separate treatment or hospital tank, if possible, is also important. However, this is often a nuisance and in many cases the entire aquarium population is diseased.


(a) Since there is conflicting evidence regarding the safety of formaldehyde to biological (nitrifying) filtration, all long-term bath treatments with Formalin·3 may (at the user’s discretion) be done in a separate hospital or treatment tank.
(b) Remove granular activated carbon from all filters used on the treatment tank; clean or change the mechanical filter media (i.e., filter floss), and return the filter(s) to service (minus the carbon).
(c)Make a partial water change of approximately 25%
(d) Depending upon the condition of the fishes needing treatment (i.e., the severity of the disease, involvement of the gills and the degree of debilitation), the dosage should be varied from 1 to 2 teaspoons per 10 gallons (10 to 20 ppm.) Severely diseased or debilitated fishes should be treated at the lower dosage.
(e) The treatment may be repeated every 24 hours, by repeating all of the above steps, including the required water changes.
(f) The dosage may be increased as the condition of the fishes being treated improves.
(g) If the fishes were removed to a separate tank, the original aquarium or pond should remain devoid of all fishes for a period of at least 4 days to insure all of the remaining infestation has expired.


(a) To a clean, non-metallic container (i.e., a plastic bucket), add one or more gallons of fresh tap water treated with Kordon’s AmQuel . For marine fish use freshly prepared saltwater adjusted to the same specific gravity (or salinity) as in the original tank. Make sure the temperature in the container is identical to that in the aquarium
(b) Add 1 to 2 teaspoons of Formalin·3. This produces a concentration of 100 to 200 ppm. formaldehyde.
(c) Agitate the solution with an airstone and adjust for a moderately strong flow of air.
(d) Remove the fishes to be treated and deposit them in the container for a treatment period of not more than 50 minutes. Immediately after the treatment period, or if signs of distress are noted, remove the fishes to a previously prepared recovery tank. The fishes may be returned to their original tank, but the presence of the original disease-causing agents in the tank water may result in a reoccurrence of the disease condition.
(e) Observe recovering fishes. Make sure that tankmates do not molest them during recovery.
(f) Repeat treatment as needed, every week. Each treatment is very stressful to the treated fishes. Do not reuse the dip solution.

If you are going to use the formalin to treat your seahorses, Red, please copy the following URL and paste it in your web browser. It will take you to a webpage with additional information about Formalin 3, and you should read through the information there before you begin the treatments:
‹close quote›

Okay, that’s the quick rundown on how to treat seahorses using formalin safely and effectively, Red.

If you can obtain it, you may also want to consider treatment with a product called FormaGreen, sir, as discussed below:

The FormaGreen is a little different than standard formalin, since it is a combination of formalin and malachite green, so the directions I’ve provided for you earlier no longer apply. Use it according to the directions on the label:


USE: external fungicide, external protozoacide, and ectoparasites, monogenia (i.e., trematodes), Hirudinea and crustacea (e.g., argulus). Helps to protect wounds from secondary infections. Can be used as a dip or for longer baths according to parts per million.

DOSAGE: for aquariums, use 2 drops per gallon. Treat one time and leave in the water for 5-7 days. Not for use with scaleless fish.

In this case, it may be beneficial to use the FormaGreen rather than the ordinary formalin, since the combination of formalin plus malachite green is even more effective in treating fungal problems. So, if the thick transparent slime coat on the affected seahorse is does indeed indicate fungal involvement, perhaps as a secondary infection, the FormaGreen should help resolve the problem.

As the instructions say, you dose the treatment tank only once and then leave the medication in the water for 5-7 days without making any water changes. In your hospital tank, if the water quality indicates that a water change is advisable, do a 100% water change (replace all the water in the hospital tank with fresh saltwater) and then re-dose the FormaGreen (two drops per gallon) and leave it in the water until the seahorse has been treated for a total of 5-7 days.

Just keep the FormaGreen in a cool, dry place in case it is needed at another time.

Good luck resolving this issue, sir.

Pete Giwojna, Ocean Rider Tech Support

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