How Can I Tell If My Fish Are Sick?

Contributed by Emma Burgess

Fish are wonderful creatures, but they're very, very different from humans. With a dog, or a cat, it's generally easier for us to tell if they're ill than it is with fish. This is because we have a lot more in common with other mammals than we do with fish, so we already kind of know what to look for when it comes to disease. When your dog starts acting lethargic, retching, and whining, you're pretty sure that something's wrong, because that's (more or less) the kind of thing you do when you yourself are sick. It's not the same with fish. Which is a shame, as the sooner you establish that something's wrong with your fish, the sooner you can mobilize your resources to heal it, and the greater your fish's chances of recovery. Unless you're very, very used to your fish's "normal" behavior, it's hard to know what to look for until it becomes very obvious, or (sadly) until it's too late. Here are a few pointers in the basic signs of general fish illness. Please note that this is by no means a definitive guide, and many illnesses display none, all, or only a few of these symptoms:

First, Establish What's "Normal"

One of the best ways to work out whether or not your fish is sick is to compare its current behavior to its normal behavior. Of course, in order to do this, you first have to know what "normal" is. This means taking some time out of each day to properly observe your fish, and take note of their activity levels, appetite, behavior patterns and so forth. This may sound tedious, but it could give you a head start in spotting when something goes wrong. A deviation from "normal" behavior is often one of the first signs of illness. But you're likely to miss this sign unless you know how your fish behaves when it is healthy.

Decreased Activity

Just like any other creature, fish conserve energy when they're ill. They need all of their resources to fight off whatever's infecting them. They therefore put a lot less energy output into swimming about. Sick fish are liable to lie at the bottom of the tank for prolonged periods of time. If they do swim about, they'll be slow and lethargic. Confusingly, however, inactivity is not always a sign of illness. If you have a fish which spends long periods of time in hides, it may simply be wary of the other fish, or feel unsafe in a wide, hide-free expanse of tank. If a "lethargic"fish darts quickly and easily for cover when disturbed, it is more likely to be feeling vulnerable than it is to be feeling ill. However, if providing it with more shelter (and perhaps removing aggressive fish to a different tank) does not help, it might be time to take a closer look.

Changes In Scale Color And Condition

Sick fish are often duller in appearance than normal. Brightly colored fish may decrease in vibrancy. Paler fish will appear grayish. Scales may flake, and some sick fish may even rub their scales off on the sides of the tank or on their tank furniture. In some cases, the scales of sick fish will raise as its body swells, giving the fish a "prickly" appearance. All in all, they look pretty rough. If your fish is not as pretty as it usually is, keep a close eye on it. Dullness, poor scale condition, scale abnormalities, and a general lack of vibrancy is often a good sign that there's something awry with your fish.

Peculiar Behavior

This final point brings us back again to the first point. If you know what is "normal" for your fish, you will be able to spot abnormal behavior. If your fish is behaving erratically, lethargically, or otherwise contrary to its usual patterns, it may well be ill. If it is spending a lot of time "gulping" at the top of the tank, it could be an indication that it"s having trouble breathing. If it"s spitting out food, not eating, or eating voraciously, these are also good signs that something is wrong - but only if it's not "normal" for your fish to do so. Once you've established a "baseline" for your fish, any deviations from that "baseline" are worth investigation. In many cases, changed tank conditions will be the culprit - and these are either easily rectified or the fish will adjust. Sometimes, however, the problem will be more serious, in which case you need to take action - not only for the sake of the sick fish, but for the sake of all the other fish it could potentially infect.