How long has the tank been set up then? What size is it and what fish, and how many, are in there?
If the tank is only a month old it will be cycling and ammonia burns are a probability. How often are you doing water changes? These will help the ammonia levels.
You can buy test kits from your lfs, or some do the tests for you for a small fee. You need to know pH, nitrite, nitrate and ammonia levels.