The biological section of a filter contains bacteria which breaks down Ammonia (NH3) to Nitrite (NO2) then to Nitrate (NO3). NH3 is toxic sewage and even at low levels can kill fish. To eliminate this, mother nature has produced NITROSOMONAS bacteria which grows on the filter media.This bacteria dies in cold winter conditions.When the temperature is increased, i.e spring time, we start feeding our fish, which increases the NH3 content of our water, what goes in, must come out! This stresses our fish, which in turn makes the immune system more vulnerable. With the increase of temperature of our water, the harmful bacteria/protozoa start to multiply.
Now you can see the problem......
Water test kits - these are not a gimmick. You cannot see the Ammonia in the water. It must be tested for.
Filter Boost - This is not a gimmick. Filter start/boost acclerates the growth of bacteria on your filter. If left to mother nature, this can take up to 12 weeks.