starting from scratch :/
so my whole tank went down eventually after an unknown outbreak of something, nothing helped and all the fish were lost sadly. Now I changed all of the water in the tank replaced all the filter media besides the biological filter and its been running for about a month i suppose. My question is , is the biological filter still strong, or is it non existence. I'm asking because i'd like to start buying new fish again but im not sure what the situation is with my biological filter.