Review on 🐠 Marineland Bio-Filter Balls - Enhanced Biological Aquatic Filtration, Designed for All C-Series Canister Filters (Pack of 1) - 90 Count by Brianne Young

I've been using them in aquariums and goldfish ponds for years to give bacteria room to grow. Your size is just right for a ten or so behind the filter pad and back of my outboard filter. . I like doing this because it encourages bacteria to grow on the balls and not the replacement pads. When pads are replaced, they help carry the bioburden. They also help with undetected dead snails or fish releasing ammonia. I see it as insurance, because the more bacteria can live and possibly multiply, the better. They really shine in an external filter. Fill your basket with it and you're done. I like that they let water through and let most of the waste go into the filter mat. There are many filter media options out there, but for the price and quality I have a hard time beating them. A box is a lifetime supply and I highly recommend it.