There is no specification like that in regards to filters! It's how many fish can a tank house. You need one gallon of water for every inch of fish if we are talking community fish like tetras or guppies. For fish that grow to 3" or more, like mollies, swordtails, etc., double that amount. And for large goldfish, cichlids, catfish and so forth, a minimum of 3 gallons per inch is recommended. The other consideration is how much food is being fed, and how frequent, if at all, are the partial water changes. For a tank with a filter that uses a medium sized cartridge, the tank should have 2-5 small fish only, and receive a weekly partial change of 25%, unless it is a 10 gallon, then it could go to every other week.
Brown water can also be due to driftwood or mopani wood if you have either in the tank.
Date published: 2018-09-25