Cool. You shouldn't need to clean it every month, only once every 6-8 weeks if you have fine filter wool. If you are using coarse sponge, once every 3 or so months should be fine. If you over-clean the beneficial bacteria may struggle to become established. If you are needing to clean your coarse sponge every month, then something is wrong.. Sorry to hear that. Did he have any signs of disease? No more than two weeks and you should be fine. Return to recommended dose after that for a while and see how you go.