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Fish Mystery Disease

Don't fall victim to one of the most common afflictions of aquarists: imaginary fish disease syndrome.

By Stephen M. Meyer

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Q. I have been a fishkeeper for the past 30 years. Tropical fish have flourished and reproduced in my freshwater aquariums innumerable times. Some have attained a very ancient (for fish) age.

About four years ago I decided to dedicate a freshwater aquarium to fancy goldfish. I set up a lovely 50-gallon aquarium complete with biological, mechanical and chemical filtration. I have never had more than five orandas or ryukin in this aquarium. I feed small amounts of flake or pellet goldfish food three times a week. I do a 30-percent water change every two weeks and I do a complete cleaning of the f every two months.

Despite all this, I lose goldfish on a regular basis. I have now quit buying orandas and I medicate the aquarium with Paragon II every two months. I have also added a live aquatic plant on which they can feed. I think these fish are simply loaded with internal parasites and that we begin at a disadvantage when we buy them.

I want to breed the fish but I am afraid their parasites might invade the eggs. Is this a danger?

A. Let me answer your questions in reverse order. You do not have to worry about internal parasites invading your goldfish eggs because your goldfish problems have nothing to do with internal parasites. I hope you won't be offended when I tell you that you have fallen victim to one of the most common afflictions of aquarists: imaginary fish disease syndrome.

Imaginary fish disease syndrome is a serious problem among hobbyists — beginners and advanced alike — and has grave consequences for their fish. It is a direct result of aquarium books that list specific diseases in an encyclopedic fashion without any indication as to the relative likelihood of actually encountering any of them.

For example, you are never told that the external parasite Ichthyophthirius that causes "freshwater ich" or "white spot" disease is virtually ubiquitous to the fish environment. Or that its coldwater form produces signs that look exactly like the very rare "carp pox" virus.

The dreaded spring viremia of carp virus (Rhabdovirus carpio) has never been seen in North America. Yet every year I get dozens of calls from people who swear their koi have this disease. Why? Because they read about it in a book.

Imaginary fish disease syndrome is also the result of the hyper-commercializing of many so-called fish medications. (Did you ever wonder why every fish drug on the market claims to cure fin rot?) If there is a drug that "cures" a problem, your fish should actually have that problem. But you have to know what the problem really is, first.

Most fish health problems have the same basic symptoms — lethargy, refusing to eat, swimming problems, bloat — so diagnosis is hit or miss without microscopic examination. The unfortunate fact is that most fish die from inappropriate care; bacterial and parasitic problems are usually secondary, if present at all.

Your goldfish deaths can be accounted for by two very simple phenomena. In the beginning, it is possible that your goldfish died from new freshwater aquarium syndrome. Despite your long experience with tropical fish you may not have considered that even a single small goldfish may excrete considerably more ammonia than a half-dozen tropical fish. Five goldfish in a new 50-gallon aquarium could poison the water. If the nitrogen cycle had not been completed, either ammonia or, more likely, nitrite poisoning may have caused the deaths during the first two months.

But it is also clear to me that your goldfish may have been starving to death. Feeding five goldfish a few flakes or pellets three times a week guarantees that some eat on each occasion and others never eat. Notice that your improved success dates from the introduction of live plants for the fish to nibble on.

Goldfish need to eat. Young goldfish should be fed about 3 to 5 percent of their body weight each day. Five small goldfish might weigh a total of 30 grams. This means that they should receive around 1 gram of fish food per day, split into several feedings. You may have been feeding this amount per week! We feed our goldfish three, sometimes four, times a day — every day. And even then they beg for fish food in between.

In winter, we cut back about 50 percent — two small feedings for fish kept indoors at room temperature. The fish in our sunroom pool, where temperatures stay around 50 degrees Fahrenheit are not fed until water temperatures rise above 55 degrees Fahrenheit.

I'll bet if you improve your feeding regimen your fish will live longer. The idea of live plants to chew on is excellent and will greatly improve aquarium conditions. The water change schedule you follow is fine for an established freshwater aquarium. But during aquarium break-in you would have had to change 50 percent per day to dilute the ammonia/nitrite.

Finally, Paragon II may indeed have its uses in cases of true parasite infestation. However, you are exposing your fish needlessly to low doses of toxic chemicals on a regular basis.

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