I kept them in the filter for probably 3-4 weeks-then actually moved them to a breeder box within the 5 gallon tank until they got round. Then they went into the 5. With a pipette I never cleaned the filter but often just blew the BBS on the floor around and it also usually got eaten too. Dead fry were removed with the pipette too. I never did BBS by the drop. I just took the hatching strainer from the Artemia Hatchery and dipped it in the coffee filter. Way more BBS than fry but I was only feeding 4 times a day.. If I had to guess why I was losing a few fry still, especially days 5 thru10, my guess would be they were eating unhatched BBS eggs. GOOD LUCK.