Looks like your tank hasn't cycled yet. If you buy an ammonia tester, you will most likely find that those levels are probably nearly off the charts.
Conventional freshwater systems depend on the nitrogen cycle to keep ammonia and nitrite levels down to non-toxic levels (zero). Any detectable levels of ammonia and/or nitrite is bad for your fish... these can at the least, shortern the life span of your fish, or at the worst, outright kill your fish. Putting fish in an uncycled tank can also lead to disease outbreaks. It is not very fun.
This is basically how a cycle works:
1.) Fish and decaying food produce ammonia
2.) Certain nitrifying bacteria use ammonia as food and convert it to nitrite
3.) As a result nitrites start raising in concentration
4.) Certain nitrifying bacteria (different than the ammonia consuming ones) use the nitrite as food and convert it to nitrates.
5.) Nitrates start raising in concentration
Nitrates are not as toxic to fish as ammonia or nitrites in lower concentrations. Keeping nitrate levels under 40ppm is recommended. Nothing other than plants and algae consume nitrates, so a few people add plants to their tanks. This however, is not needed. A 30-40% water change weekly will take care of nitrates.
Since you already have fish in your tank, the goal here is to keep ammonia and nitrite levels as low as possible. Get yourself ammonia and nitrite testers. You want to keep your ammonia and nitrite levels as low as you can via water changes... try keeping both levels under 0.5, lower if you can. Daily 50% water changes should suffice, but do larger ones if you want to. Since your tanks are not very large, it shouldn't be too hard. Remember to use dechlorinated water, and make sure the water going into the tank is the same temperature as that of your tank water. As long as you keep that in mind, you can literally do nearly 100% water changes, and your fish will be fine. While you do the water change, vacuum the gravel well, and try to remove as much debri as possible. During your cycle, you will notice ammonia levels will be harder to keep under control... this will last for a couple of weeks. After that, ammonia levels will continuously get lower and lower... at this point, switch, and start measuring your nitrite levels. You'll find that, like ammonia before, these levels will be a bit harder to keep under control After a few more weeks, these levels will also begin to drop. As soon as both ammonia and nitrite levels reach zero consistantly over the course of a week or so, you know that your tank has cycled.... at this point, you can start doing 30-40% water changes once a week, rather than 50% water changes everyday.
Feeding lightly should also help you a bit, feed every other day, and just enough so that your fish can finish the food in about a minute.
Its not easy... and it will require some work, but if you keep at it the rewards of keeping healthy fish will be great.
HTH
-Richer
