sick catfish

Question
Hi, I have a small fish tank (freshwater) it contains 3 zebra danios, 2 white clouds, 2 catfish and snails. Our catfish have become very listless and aren't really swimming much at all.  One has gone a bit pale and has a few red spots on it.  Just wondering what is wrong???  I have changed the water, and am keeping an eye on the temperature.  I don't know what else to do. Please help!

Answer
Good morning Glenna, thank you for your question.

Red spots on fish usually indicate flukes, red ulcers are a different story as they are indicative of water quality issues. I commend you on doing a water change, that always helps. While your tank sounds like it has a light load on it, I'm not sure what you mean by catfish. Corydoras?
http://en.wikipedia.org/wiki/Corydoras

There are many thousands of species of catfish. There are a hundred variants of corydoras, possibly more! Some are definitely more sensitive than others. Panda cories, for example, are more demanding about water quality than their hardier bronze/green brethren.

The first thing you should do is test your water with a test kit. Liquid test kits provide better accuracy and value over strips. Ammonia and nitrites must be 0 ppm at all times, nitrites should be no higher than 20 ppm. Make sure these levels are at acceptable ranges, effect water changes twice daily (up to 20% each time) until they are so.

You don't mention how small your tank is, I hope it's a 10 gallon. Anything less will not provide the room that the schooling fish need, and I have not seen cories thrive in tanks less than 10 gallons. Make sure you are using a fine substrate, they can damage their barbels on sharp substrate such as polished glass chips. They also do not appreciate a river rock of too large a diameter, such as pea gravel.

I would not medicate at this point. Get back to me with those water test results - if all levels test fine, you may need to treat with Fluke Tabs, but not at this juncture.

I hope that helps, have a nice weekend!
Nicole