Fish Keeping 101 ~ a collection of articles aimed towards the aquarium fish beginner, but with useful information for everyone.

Common Diseases

There are a lot of infections and parasites that can afflict our fish. Many of them will never be encountered by the average aquarium hobbyist, and if something unusual does show up in your tank, chances are that you would probably never know for sure what hit you. There are however several which appear commonly in aquaria, and a few of them are even easy to diagnose.

First, watch how your fish behave. If you notice your fish doing strange things, there is probably a reason for it. There are some behaviors you don’t need to worry about, at least from a health standpoint. If your fish is ripping out the decorations or seems to be trying to break the glass, he’s probably just bored. If two fish seem to be at each others throats, they are probably either fighting or breeding. Just watch to make sure nobody gets seriously injured. Stress and illness can cause more worrisome behavioral changes that you should pay close attention to:

Eating—While it is not uncommon for a new fish to fast for a day or two (some more exotic species may even go a couple of weeks), if a fish who has previously eaten suddenly stops, it’s time to worry (unless of course it’s a female mouth-brooder with fry). Worry even more if the fish even refuses treats such as live or frozen foods. Not eating may indicate that an internal parasite is present, or may just be a sign that the fish doesn’t feel well.

Clamped Fins—Another sign that a fish doesn’t feel well is that he holds his fins tight against his body. Again, this won’t tell you what the problem is, but will clue you in to the fact that something is not right. (Note: some fish normally keep their fins down when they are not swimming.)

Hiding-Some fish are habitual hiders, but if they miss several feedings, you can start to worry. If a fish who is normally out where he can be seen, suddenly disappears (and can’t be found on the floor outside the tank) he is probably sick, stressed, or breeding. Keep an eye on him.

Sitting on the Bottom-Regular bottom dwellers don’t count here. If a mid- or top-water swimmer starts sitting around on the bottom of the tank he probably doesn’t feel well.

Swimming in the water flow—If your fish are hanging out near your filter and swimming against the flow, they don’t feel well. Check for other symptoms.

Breathing—Rapid or labored gill movement, or gasping at the surface are indicators that your fish is having trouble breathing. This is a serious concern because whether your fish is infected with some parasite or is simply suffocating due to poor water conditions, the result will be the same. First, check your water. If you have high levels of toxic substances you want to correct the problem as quickly as possible to avoid serious gill damage. If the water checks out, take a look at your bio-load. If there are a lot of fish in the tank, you may just be a little low on oxygen. Try adding supplementary aeration. If the fish don’t look better within several hours, you may have a gill parasite. Treat with appropriate medication.

Erratic Swimming—Fish is turning in circles. Probably damage to the nervous system. Not much to be done here. Dispose of the fish to limit the spread of causative organism and keep an eye on your other fish.

Abnormal Position—If your fish is holding its body in an abnormal position and seems to have extreme difficulty righting itself, there may be a swim-bladder problem. (Note: fish orient themselves to the light source, so if there is a stronger light coming in from the side than from the top of the tank, this may be the cause of tilted fish).

Shimmies-If your fish appears to be swimming in place, check your water quality and make sure all conditions are correct. Also check for other signs of illness.

Scratching—If your fish seem to be scratching themselves against the gravel or decorations in the tank, they probably itch. Itching is often caused by external parasites. Try medicating.

On to part II physical indicators-->