The filter is just 4 sponges in a plastic rack and i change the top sponge/filter once a week.I bought the fish from a garden centre so the 60L tank, and pump and heater all came together.I have the temp exact at 26 degrees but i dont have anything to test the water....are we talking PH test..?Plus, i have two bottles of something which i empty a cap full in once a week.???