If you are new to keeping tropical fish you should find out as much as you can about looking after them. One thing you need to understand is some basic water chemistry and how to keep the conditions in your tank ideal for your fish. You should purchase a water testing kit for use in both cycling the tank and routine maintenance that contains testing strips for ammonia, nitrites, nitrates, pH, chlorine and chloramine.
Some Definitions to Help in Your Understanding of Water Chemistry
Aerobic and Anaerobic bacteria – aerobic means with oxygen, anaerobic without. basically bacteria that can thrive in either conditions with or without oxygen.
Ammonia – this is a toxic material produced by the fish which will kill them if allowed to build up. Nitrifying bacteria convert it first to nitrites, then to nitrates which are much less harmful.
Chlorine and chloramine – water companies add either chlorine or both chlorine and chloramines to tap water to kill any organisms but they are both harmful to your fish. Chlorine can be removed by allowing the water to stand for a day or two but chloramines must be removed by using a chemical purchased from your pet shop.
Copper – this can be present in tap water if you have old, corroded pipes and is also an ingredient in some fish medications. For tropical and marine fish this is not usually too much of a problem but if you have an invertebrate tank you must be careful not to have any copper in the water as many invertebrates are very susceptible to it.
Nitrites and nitrates - nitrites are produced by nitrifying bacteria form the ammonia excreted by the fish. They are also toxic but are then converted into nitrates which are less harmful. However they should still be removed regularly by doing partial water changes.
pH – pH is a measure of how acidic or basic the water in your tank is. A pH of 1 is very acidic, a pH of 14 very basic. Neutral water has a pH of 7.
Phosphates – phosphates are good fertilisers so if you have a high level in your tank you will encourage the growth of algae. They can be introduced in tap water, food or by plants that are rotting.
Salinity – this is a measure of the salt (sodium chloride) content of a tank and is important if you have a reef tank.
Hardness – hardness measures the amount of minerals dissolved in the water, particularly magnesium and calcium. For freshwater tanks, unless the water is exceptionally soft, it is not really important but can be an issue in invertebrate tanks as some invertebrates an all corals need these minerals for growth.

