are my fish sick

Question
I have tropical fish and they have been healthy and now all of a sudden they seem sick. They swim around the tank very fast and chase each other and they are the same kind of fish.

Answer
Good morning Sarah, thank you for your question.

I couldn't say whether your fish are sick. There could be lots of reasons why they're chasing each other.

If they are feeling crowded, then they might be chasing each other because they feel uncomfortable. That's one reason not to put too many fish in your fish tank. You don't say how big your tank is (in gallons), how many fish you have, and what kind they all are, so this may not be the case at all. I can't tell, based on the information you've given me.

They could also be feeling frantic because the water quality is poor. No matter what size your tank is, it is agreed that weekly water changes are very good for your fish. So change 10-20% of the water a week, using tap water treated with dechlorinator. This, along with gravel vacuuming twice a month and changing/rising your filter weekly or twice a month, will ensure your fish never get sick from being in water that has ammonia or nitrites in it.

Speaking of, have you tested your water? A master liquid test kit offers the best value and accuracy, but no matter what kind of kit you are using, it will tell you if ammonia or nitrite is present in your tank. These levels are toxic if they are detectable! Again, there is no "safe" level of ammonia or nitrite. 0 ppm is the only level that is safe. Nitrates, on the other hand, can be as high as 20 ppm.

So in conclusion, Sarah, test your water with a test kit when you find your fish are acting strange. Or, if you know you haven't been doing weekly water changes, or have skipped some other part of regular maintenance, do what you need to do to make the tank look and smell clear and healthy. I always say, a healthy aquarium should smell earthy, like wet soil, slightly sweet. Never sharp or bitter or rancid.

I also encourage you to research the kind of fish you have (whatever kind it may be) to make sure you are feeding it the right things (variety is key), not overfeeding, and not introducing the wrong tankmates. Most important is that you have it in the right sized home. For example, if you have a 29 gallon tank and have 5 bala sharks in it, that is bad news. Use Google to research the kind of fish you have.

Also, check out both of these sites for future reference:
http://freshaquarium.about.com
http://www.wetwebmedia.com

Both sites are searchable and have lots of info to offer.

Take care,
Nicole