Re:Seahorse swollen eye

Pete Giwojna

Dear Judy:

I’m very sorry to hear that the seahorse with exopthalmia was unable to recover. That makes me think that it was indeed an underlying bacterial infection that caused the Popeye and ultimately killed the seahorse. All my condolences on your loss!

It is a very sensible precautions to prepare a medicine chest or at least a first aid kit consisting of useful medications to have at the ready when trouble arises. Prevention is our first goal but is not always possible to achieve, of course, and when disease problems do crop up, early detection of the problem and prompt treatment are the keys to restoring health. Some diseases are remarkably fast acting, such as pathogens and parasites that multiply by binary fission and can quickly explode to plague proportions when conditions favor them. By the time a health problem becomes apparent, there is often no time to make the rounds of your local fish stores searching for the right medications, much less time to order the meds you need through the mail.

Savvy seahorse keepers avoid such delays by keeping a few of the most useful medications on hand at all times so they’re right there when needed. For the greater seahorses, the following weapons should be in your disease-fighting arsenal at the ready, and I strongly suggest you stock your fish-room medicine chest will useful: first aid preparations such as methylene blue, a pouch kit; potent antiparasitic agents such as formalin and metronidazole; a good antifungal agent; and broad-spectrum antibiotics. And don’t forget the heavy artillery for emergency situations when you’re not sure what you’re dealing with — combination drugs with ingredients that are effective against protozoan parasites, bacteria, and fungal infections alike. I would be happy to recommend some must-have medications all seahorse keepers should keep on hand with you, Judy. For example, a basic seahorse First Aid Kit might include the following items:

Methylene Blue (for reversing nitrite poisoning and relieving respiratory distress);

Formalin (for treating ectoparasites and fungal problems);

Antiparasitic for treating internal parasites (i.e., praziquantel or metronidazole);

Broad-Spectrum Antibiotics (e.g., kanamycin sulfate and/or doxycycline for treating bacterial infections);

Small Syringe with Needle and Cannula (pouch flushes, tube feeding, needle aspirations);

Diamox (i.e., acetazolamide for treating Gas Bubble Disease);

A good combo drug (e.g., Furan2 or Nitrofuracin Green) for when the diagnosis is uncertain;

Vibrance (includes beta-glucan to boost the immune system and help prevent disease).

Having these items on hand will allow you to address nearly all of the common afflictions of seahorses promptly and effectively, as discussed below in greater detail:

Must-Have Meds

methylene blue

Commonly known as "meth blue" or simply "blue," this is a wonderful medication for reversing the toxic effects of ammonia and nitrite poisoning (commonly known as "new tank syndrome"). Since hospital tanks are usually without biological filtration, and ammonia and nitrite can thus build up rapidly (especially if you are not doing water changes during the treatment period), it’s a good idea to add methylene blue to your hospital ward when treating sick fish.

Methylene blue also transports oxygen and aids breathing. It facilitates oxygen transport, helping fish breathe more easily by converting methemoglobin to hemoglobin — the normal oxygen carrying component of fish blood, thus allowing more oxygen to be carried through the bloodstream. This makes it very useful for treating gill infections, low oxygen levels, or anytime your seahorses are breathing rapidly and experiencing respiratory distress. It is the drug of choice for treating hypoxic emergencies of any kind with your fish.

In addition, methylene blue treats fungus and some bacteria and protozoans. Methylene blue is effective in preventing fungal infections, and it has antiprotozoal and antibacterial properties as well, by virtue of its ability to bind with cytoplasmic structures within the cell and interfere with oxidation-reduction processes. A "must" for your fish-room medicine cabinet. However, be aware that it is not safe to combine methylene blue with some antibiotics, so check your medication labels closely for any possible problems before doing so. (The Kordon brand of methylene blue is best, in my opinion, if you can obtain it.)


This is basically a 37% solution of formaldehyde and water. It is a potent external fungicide, external protozoacide, and antiparasitic, and seahorse keepers commonly use formalin to cleanse new arrivals of ectoparasites during quarantine. Formalin (HCHO) is thus an effective medication for eradicating external parasites, treating fungal lesions, and reducing the swelling from such infections. It is a wonder drug for treating cases of Popeye caused by trematodes, and also eradicates nematodes as well as bacteria.

Formalin has a limited shelf life and degrades to the highly toxic substance paraformaldehyde (identified as a white precipitate on the bottom of the solution); avoid using any formalin product that has such a precipitate at the bottom of the bottle.

When using formalin, beware that it basically consumes oxygen so vigorous aeration must be provided during treatment. It can be administered as a 1-hour bath at a concentration of 200 ppm (l ml per 5 liters of seawater or about 1/5 teaspoon per 1.33 gallons). Again, the Kordon brand of formalin is a good product for hobbyists.

Formalin is guaranteed to knock your biofilter for a loop, so confine its use to the hospital tank only!

Metronidazole (Hexamit/Flagyl)

This medication was originally developed to combat the parasites that cause amoebiasis and giardiasis in man and wreak havoc on the human GI tract (Kaptur, 2004), and it remains the treatment of choice for eradicating internal parasites (intestinal flagellates, digenetic trematodes, etc.) in seahorses. It is extremely effective in treating wasting disease (weight loss despite eating well) and loss of appetite when they are due to such intestinal parasites (Kaptur, 2004).

Metronidazole is most effective when ingested (Kaptur, 2004), and is best administered orally via gut-loaded shrimp. If administered in a hospital tank, it will be absorbed from the water through the gills.

Metronidazole is only active against anaerobic bacteria, so it is one drug that can be used safely in your main tank without impairing the biofiltration (Kaptur, 2004). This is a very safe with medication with little to no danger of overdosing.

Metronidazole can be combined safely with aminoglycoside antibiotics such as Kanamycin and neomycin to create a potent synergistic treatment that’s effective against both aerobic and anaerobic bacteria.


This is a very effective antiparasitic that works equally well against external and internal parasites alike. Like metronidazole, this is a very safe medication that works best when ingested, hence it is best administered by bioencapsulation — i.e., gutloading live shrimp or injecting them with a solution of the medication.

When treating ectoparasites, it can be added directly to the water in the treatment tank (dose one time and leave in the water for 5-7 days). However, in order to do this, it must first be mixed with ethyl alcohol (e.g., vodka) in order to make it water soluble.

Broad-Spectrum Antibiotics

If you could only keep one antibiotic in your fishroom medicine cabinet, kanamycin sulfate (e.g., KanaPlex or Kana-Pro) is the one I would choose because of its excellent solubility in saltwater and effective absorption.

Kanamycin sulfate

This is a potent broad-spectrum, gram+/gram- aminogylcoside antibiotic. It is wonderfully effective for aquarium use because it is one of the few antibiotics that dissolves well in saltwater and that is readily absorbed through the skin of the fish. That makes it the treatment of choice for treating many bacterial infections in seahorses. Like other gram-negative antibiotics, it will destroy your biofiltration and should be used in a hospital tank only.

Best of all, kanamycin sulfate can be safely combined with certain other antibiotics such as doxycycline or neomycin or triple sulfa to increase its efficacy, as explained below. If you can keep more than one antibiotic in your fishroom, make it one of the antibiotics that can be combined safely with kanamycin to produce a synergistic effect. For example, kanamycin + doxycycline is an effective combination for treating certain Vibrio infections. Likewise, combining an aminoglycoside antibiotic (e.g., kanamycin or neomycin) with triple sulfa works well for combating some bacterial infections in seahorses.

Doxycycline hydrochloride

USE: broad-spectrum antibiotic derived from oxytetracycline. Used for both gram-positive and gram-negative bacterial disorders. Fin and tail rot, septicemia, mouth rot. Will not be deactivated by high pH levels in saltwater like ordinary tetracycline. Works in a similar manner to chloramphenicol.

WATER DOSAGE: 1/4 teaspoon per 20 gallons, every 24 hours for 10 days. Do a 25% water change before each daily treatment.

FOOD DOSAGE: doxycycline may be mixed into frozen or pelletized food by using 2 teaspoons per ounce of feed. For seahorses, you’ll want to use frozen Mysis for this purpose. Thaw out one ounce of the frozen Mysis and, gently but thoroughly, mix in 2 teaspoons of the doxycycline hydrochloride after the Mysis thaws. Then put the medicated food in a Ziploc bag and lay flat in the freezer until frozen. Feed the seahorses their fill of the medicated frozen Mysis as usual once a day for the next 10 days. This makes it especially useful for treating seahorses since they can be fed the medicated Mysis in the main tank where they are the most comfortable, giving the hobbyist a stress-free treatment option for some conditions.

neomycin sulfate

Neomycin is a very potent gram-negative aminoglycoside antibiotic. Most of infections that plague marine fish are gram-negative, so neomycin sulfate can be a wonder drug for seahorses (Burns, 2002). As mentioned above, it can even be combined with other medications such as kanamycin, nifurpirinol or sulfa compounds for increased efficacy. For example, kanamycin/neomycin is tremendous for treating bacterial infections, while nifurpirinol/neomycin makes a combination that packs a heckuva wallop for treating mixed bacterial/fungal infections or problems of unknown nature.

Neomycin will destroy beneficial bacteria and disrupt your biological filtration, so be sure to administer the drug in a hospital tank.

Combination Drugs (Nitrofuracin Green, Furan2, etc.)

Combo medication — that is how hobbyists refer to the drug cocktails that combine antiparasitic, antifungal and antibacterial agents in one commercial preparation. Look for a product that combines the following ingredients in one potent mixture: antiparasitics such as nitrofurazone and metronidazole, effective antibiotics like neomycin, and kanamycin or nitrofuran antibiotics, possibly methylene blue, and antifungals such as nifurpirinol. The result is a powerful combination drug that’s effective against protozoans, fungus, and many kinds of bacteria. When combined together, these medications cover all the bases and the formulation acts as a particularly strong broad-spectrum antibiotic.

A good combination drug is the ultimate weapon in your medicine cabinet. It is effective against a wide range of diseases, making it a versatile shotgun for restoring order when trouble breaks out in your tank. When you suspect an infection is at work, but don’t know whether you’re dealing with fungus, bacteria, protozoan parasites or a mixed infection, don’t hold back — break out the heavy artillery and give the bugs both barrels! Use them with caution in a hospital tank only.

Some examples of combo meds that are commonly available in pet shops and fish stores are Furan2 and Nitrofuracin Green:


Furan2 is a good combo medication that consist of two nitrofuran antibiotics (nitrofurazone and furazolidone) plus good old methylene blue. That gives it both bacteriostatic and bactericidal properties, and makes it active against various gram-negative and gram-positive bacteria. The methylene blue stains the water in the treatment tank as and prevents the photosensitive nitrofuran antibiotics from being deactivated by light. Methylene blue is effective in preventing fungal growth, and it has antiprotozoal and antibacterial properties as well, by virtue of its ability to bind with cytoplasmic structures within the cell and interfere with oxidation-reduction processes. This makes the combination of methylene blue, nitrofurazone and furazolidone very broad spectrum and fairly potent. Furan2 is especially effective for treating mild skin infections, but serious infections such as vibriosis or marine ulcer disease should be treated with stronger antibiotics, such as doxycycline + kanamycin.

Best of all, Furan2 can be safely combined with Aquarium Pharmaceuticals antiparasitic medications such as Acriflavine to increase its effectiveness and guard against secondary infections when you are treating for parasites.

Thus, when combined with a good antiparasitic medication like Acriflavine, a good combination drug like Furan2 can be the ultimate weapon in your medicine cabinet. It is effective against a wide range of diseases, making it a versatile shotgun for restoring order when trouble breaks out in your tank.

Nitrofuracin Green

A special formula of nitrofurazone, furazolidone, methylene blue, and sodium chloride.

USE: anti-microbial, anti-protozoan, antibacterial, and anti-fungal. Wide spectrum. Good for newly arrived fish in quarantine situations. Also be good for healing wounds and ammonia burns on newly arriving fish. Widely used for shipping or packing water. Works well for sores on fish in Koi ponds.

DOSAGE: add 1/4 teaspoon of Nitrofuracin Green per 20 gallons every 24 hours, with a 25% water change before each daily treatment. Treat for 10 days.

However, for best results, the hobbyist should take special precautions when administering Furan2 or Nitrofuracin Green such as this because they are photosensitive and can be deactivated by light. That means you’ll need to darken the hospital tank while you treat the seahorse(s). Do not use a light on your hospital tank, cover the sides of the tank with black construction paper or something similar, and keep an opaque lid or cover on the aquarium during the treatments. Remove this cover from the aquarium only long enough to feed your seahorses.

You should also be aware that Furan2 and Nitrofuracin Green will cause discoloration of the aquarium water, turning it a shade of blue-green. This is harmless and can be removed after the treatments using activated carbon filtration after the treatment regimen has been completed.

Diamox (acetazolamide)

This prescription drug is an effective carbonic anhydrase inhibitor that is commonly used to treat glaucoma, hydrocephaly, and altitude sickness in human. In tablet form (125 mg or 250 mg), it is the only practical treatment for Gas Bubble Syndrome (GBS) in seahorses available to the home hobbyist. Depending on the form of GBS you are treating, it can be administered orally, as a series of baths, or as a pouch wash. It is also useful in treating cases of Popeye (e.g. exopthalmia) by virtue of its ability to help control intraocular pressure. Few medications have saved more seahorses’ lives than acetazolamide and it needs to be in your fish room.

Pouch Kit

Bloated pouch is the most common ailment of seahorses and every seahorse keeper should have the equipment needed to treat the condition on hand. This includes a small syringe with catheter, suitable eyedropper, pipette or the like for rinsing the pouch, as well as a medicated pouch-flush solution. (The small syringe and catheter are also useful for tube feeding seahorses that are on a hunger strike.) Ready-made kits consisting of special antibiotic solution, flushing apparatus and instructions are available from the Ocean Rider seahorse farm in Hawaii, or you can easily assemble your own kit from the necessary components. Acetazolamide combined with kanamycin sulfate or neomycin makes a superior pouch wash for cleansing the marsupium and stopping the formation of excess gas.

Small Syringe & cannula

Every fish-room medicine cabinet should include a small, clean syringe with a fine-gauge needle. They are indispensable for flushing pouches, tube feeding seahorses that have gone on a hunger strike, and injecting frozen Mysis or live shrimp with medications when administering them orally. Leslie Leddo finds that a 1/2 cc insulin syringe with a 26-gauge needle is ideal for such purposes. For best results, a small diameter cannula or catheter that will fit on the end of the syringe and place of the needle is especially useful for pouch flushes and tube feeding.

Okay, Judy, that’s the quick rundown of the most useful medications for the seahorse hobbyist to keep on hand. Some of the medications mentioned above are available from well-stocked pet stores or local fish stores.

And you can get a wide range of antiparasitics, anti-fungals, and antibiotics, including pretty much all the medications on my list without a prescription from National Fish Pharmaceuticals (aka the Fishy Farmacy) at the following URL:

Click here: Fish Medications

Diamox (the tablet form of acetazolamide) will be the toughest of the most-have medications to obtain, since it’s a prescription drug. Most hobbyists will need to obtain it via their family physician or local veterinarian.

If neither your Vet or family physician will prescribe Diamox for a fish, as is sometimes the case, then there are places you can order Diamox online without a prescription, but save that for a last resort. (You can’t always be certain of the quality of the medications you receive from such sources; in some cases, you even need to be concerned about counterfeit drugs, although Diamox certainly shouldn’t fall into that category.) The medications will take a week or two to arrive, which is troublesome when your seahorse is ailing and needs help ASAP. And, as you know, customs officials can confiscate such shipments, although that very rarely happens with this particular medication.

If you ultimately need to go that route, Judy, the following source is the one most seahorse keepers have found works best:

Click here: Inhouse Drugstore Diamox – online information

They offer 100 tablets of Diamox (250 mg) for around $20 US, but they ship from Canada by mail, which usually takes a little under two weeks for delivery. That’s why it’s best to plan ahead and line up the medication now, before it’s actually needed.

Having the items above in your medicine chest, ready to use, will enable you to respond to almost any emergency or disease problem that may arise quickly and efficiently.

Best wishes with all your fishes, Judy!

Pete Giwojna

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