http://forum.aqua-fish.net/ A forum devoted to aquarium fish, plants, techniques and fish keeping as a whole. en http://forum.aqua-fish.net/?topic=basic-water-testing#1 When you are first starting up your aquarium , water testing is a must so that you can monitor at what stage your tank is in its initial cycle The first test required is for ammonia levels-ammonia is produced by fish waste,uneaten food etc and too high a level can be very toxic to your fish.As the tank cycles bacteria will convert the ammonia to nitrites which is less toxic Ideal ammonia level is 0 the second test required is for nitrites,less toxic to the fish but still not healthy for the tank. Ideal nitrite reading is 0 Eventually bacteria in your filter and water will convert the nitrites to nitrates,the only way to remove these from the tank is by regular water changes. Ideal nitrate reading is 0 but normally they can reach higher just before a water change takes place. If ammonia or nitrites are showing a reading then the tank is not fully cycled. mickey 2008-05-06