 Nitrate test kits are used to determine how much nitrate is in your aquarium. It is very useful to know how much nitrate is in your aquarium as this is one of the main causes for algae. The process for nitrates starts with ammonia which gets broken down to nitrite then to nitrate. Nitrate is a common food for aquarium plants and algae.
If you use a nitrate test kit then you will know how much is being produced and whether of not you need to add more plants of fish depending of what you want to achieve. If algae are your main problem then I would use a nitrate remover and algae killer but more importantly I would do regular water changes and get more plants for your aquarium.
Nitrate will not harm your fish unless it goes through the roof and by it being lower you will have a much less stressful environment. In general I aim to keep my nitrates below 5 - 10ppm and test every 1 to 2 weeks to make sure I can catch them before they creep up and I get a really annoying algae bloom.
We have a large selection of nitrate test kits which are readily in stock and well worth keeping on hand avoiding one of the messiest problems available. | 
