Dear FishFace:

Pete Giwojna

Dear FishFace:

Over the past 25 years I have encountered several instances of blindness in seahorses, sir. Two of them were the result of severe bilateral exophthalmia (commonly known as Popeye), which caused functional blindness and prevented the seahorses from feeding properly. In a few other cases, the apparent blindness was associated with high intensity lighting.

In short, I know of a few seahorses that have developed blindness and it’s not as uncommon as you might expect. Some of the marine fish that are especially prone to this problem in captivity are lionfish, large angelfish of various species, seahorses, clownfish, and large puffers and porcupine fish.

In most of the cases I am familiar with, the blindness was caused by exposure to bright lighting under circumstances when there was no way available for the fish being displayed to seek shelter and get out of the light when they wanted. When that’s the case, the blindness is often temporary, and the affected fish’s vision can be restored by maintaining it in total darkness for an extended period of time. Apparently the complete absence of light is beneficial or therapeutic in some cases of blindness, and the affected fish are normally hand fed well they are recovering…

For example, this is what Robert PL Straughan (Saltwater Aquarium in the Home) reports regarding blindness in aquarium fishes, FishFace:


“When a fish suddenly shows no interest in food, it may have gone blind. Excess light is usually the cause, especially when the fish is not given a dark hiding place in the aquarium where it can go once in a while. The fish may bump into coral or snap at food which it can feel or sense but cannot see, and prompt action must be taken to save your pet. You can usually see if the fish is blind by moving your hand quickly in front of the glass. If he shows no response even though you attempt to frighten him from the outside, and if he swims to the end of the aquarium and bumps into the glass or coral, then he is most likely blind. This does not necessarily have to be a permanent condition and it can usually be cured, with time and patience.

“First remove the victim to a separate aquarium, and cover the sides and top of the tank with cardboard to keep out most of the light. Since the fish is blind, it will have to be hand fed and this may be accomplished by holding the fish gently with one hand and forcing chunks of chopped shrimp into its mouth with the other. Usually, if the fish is tame, it will accept food eagerly in this fashion and if it does, it is well on the road to recovery. Usually when hand feeding a blind fish, it is best to handle the fish very gently so that it will not become excited, then release it equally as gently after the food has been placed well in its mouth. It will usually swallow the food and the whole procedure may be repeated until the fish has eaten his fill.

“If, after a week or so, the fish responds to light, remove one side of the cardboard so that the aquarium will be partly lighted. The fish may be returned to the regular aquarium after its sight has returned, but this time, it should given a good coral hiding place so that it can get completely out the light when it desires. This is a perfectly natural situation as anyone who has observed marine life on the reef can testify. The fish will swim out into the bright sunlight for brief periods of time and then periodically retreat to the dark seclusion of a coral ledge or other protection.

“Large Porcupine fish, Rock Beauties, and Angelfish, are especially susceptible to blindness from too much light, and can be blinded in a matter of hours if left in direct sunlight with no cover or protection. Also the Lionfish, Clownfish, Seahorse and any other fish which tend to stay out in the open, can be blinded if subjected to intense aquarium light.” This condition is often brought on, when fish are placed on public display. The lights are left on for long periods of time, and the fish are given no place to hide so that usually in a week or so, the fish are blinded.”
Robert P.L. Straughan, The Salt-Water Aquarium in the Home, A.S. Barnes & Company, 123-124.

So marine fish can be blinded by intense light if they have no opportunity to escape from the bright lighting for an extended period, and our prize ponies are among the fish that are most susceptible to this problem, FishFace. Seahorses with impaired vision stop feeding (they are of course visual hunters) and typically stop moving around since they cannot see where they are going to avoid obstacles.

However, from what I have gathered, the blind seahorses I know of all readily accepted handfeeding and seemed to realize that the hobbyist was trying to help them by offering food in this manner.

So if you have recently changed your aquarium lighting, especially if you have upgraded to high-intensity lighting such as metal halides for the sake of live corals or some such thing, it is possible that Hershey may have gone blind, FishFace.

But blindness would not account for all of the symptoms you have reported, sir, and I strongly suspect that Hershey has contracted an infection of some sort as well. Very likely, it is the same affliction that claimed the life of the older seahorse you mentioned in the past.

I would recommend treating Hershey with broad-spectrum antibiotics in isolation in your hospital tank or quarantine tank, FishFace. If you want to keep the treatment tank darkened while you are administering the medications to see if that is helpful for the blindness, that’s not a bad idea.

The antibiotics I feel would be most helpful for a case like this are doxycycline used in conjunction with kanamycin sulfate, as explained below:

Doxycycline hydrochloride

USE: broad spectrum antibiotic derived from oxytetracycline. Use for both gram-positive and gram-negative bacterial disorders, including fin and tail rot, septicemia, and mouth rot. Unlike tetracycline antibiotics, it will not be deactivated by the high pH levels found in marine aquaria. Works in a similar manner to chloramphenicol.

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

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. Kanamycin can be combined safely with certain other antibiotics such as doxycycline or neomycin (as well as metronidazole) to further increase its efficacy. Like other gram-negative antibiotics, it will destroy your biofiltration and should be used in a hospital tank only.

USE: gram-negative bacterial infections and resistant forms of piscine tuberculosis (mycobacteria). Works especially well in saltwater aquariums.

DOSAGE: add 1/4 teaspoon per 20 gallons. Treat every 24 hours and perform a 25% water change before each treatment. Treat for 10 days. (When treating piscine tuberculosis, treat for 30 days.)

Both the doxycycline and kanamycin can be obtained online without a prescription from National Fish Pharmaceuticals at the following URL:

That’s what I would recommend at this point, FishFace. Isolate Hershey as soon as possible for the sake of the other seahorses and treat the pony with a full regimen of broad-spectrum antibiotics in your hospital tank or quarantine tank. Keep the tank darkened throughout the treatment period, as described in the discussion on blindness, and continue to attempt to hand feed the seahorse.

I am in the process of preparing a more detailed response for you that will address the periodic losses you have experienced with the seahorses in your main tank, sir, but that’s a more complicated matter. I’ll try to get that response to you as soon as I can, hopefully by tomorrow…

Good luck!

Pete Giwojna, Ocean Rider Tech Support

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