Cloudy eyes and Tail rot?

Question
 My brother is having a problem with his freshwater tank.  His fish have cloudy eyes and tail rot.  Can you help?

Answer
Hi Jeff,

The problem is definitely water quality. A freshwater test kit would show that his tank has ammonia or nitrites present (when both these levels should be 0 ppm) and if not these, then probably high nitrates - these should be <20 ppm.

The question is, WHY is the water quality poor, and what, if anything, can be done to fix it? There are lots of things that can be wrong. His tank might be brand new, in which case it hasn't "cycled" - has not matured, and is not ready for fish yet since the beneficial bacteria are not present in the tank at concentrations high enough to support life. Even if the tank is not new, the beneficial bacteria could be overwhelmed and unable to function. He may not be changing enough water, he may have too many fish in too small a tank, he may have been overfeeding the fish, causing pollution. Or it may be a combination of all these factors.

Have him read this to get an idea of what an aquarium entails: http://www.firsttankguide.net/steps.php
This website covers all the basics, and should help.

There's also these articles:
http://freshaquarium.about.com/od/aquariumstartup/Aquarium_Startup.htm

When he gets his water quality where it should be, he can start thinking about how to medicate these fish. There are lots of finrot/popeye remedies out there for fish, but using the medication is useless until he gets the water quality fixed. Remember, fish live in the water, it's their environment, just like our air. If you were sick from carbon monoxide poisoning, I couldn't start treating you until you were exposed to healthy air.

If you write back with some details, like the size of your brother's tank, what kind of fish he has in it, what he feeds and how often, and also what he does for maintenance - I could help you further. When does he change the water and how much? And how about the filter, when does he clean it or replace the disposable media? All these things are needed in order to figure out what the problem is, and correct it.

Get him to get his water tested at the pet store or fish store, or better yet, encourage him to buy some testing strips so that he can check his aquarium water himself.

Setting up an aquarium is a little bit complicated at first - at least, it's not as easy as it seems. As I always say, people who keep cats usually do it right the first time. They have obvious needs - they need a place to go to the bathroom, a food bowl and a water bowl. They will probably live a long time without further care. However a fish tank is more like a science project, because these creatures don't breathe air, they live in water - and they can't communicate their needs, you just notice when they are already sick. Their water may not be obviously dirty the way a litterbox is dirty. So some reading is required...

Anyhow, I hope that helps. Feel free to write again!
Nicole