i just started over last monday on my 20hg tank ammonia nitrate and nitrite at 0.0 ppm with 2 corys and 4 days after i added another cory and i tested the the water the day after i added the new cory the ammonia was at 2.0 nitrate and nitrites sre at 0.0 ppm and the water was clear and now for a few days the waters been cloudy and i noticed today there is like rust looking spots on the back of the tank and the filter is cloging up slowly so im wondering am i doing anything wrong or am i suppost to let the tank go or what i want to do it right this time ya no