Hello- I have a 29 gallon established tank with several mollies, tetras, swordtails, pleco and crawfish. I was running 2 HOB filters for a while but have stepped up to an eheim classic 250. Huge improvement btw but not the point of post. Do I need to temporarily keep one of the HOB filters in place to acquire beneficial bacteria in canister or is there enough in the rocks, artificial plants, etc? Thanks for responses.