These are sold as safe for fry when in fact, they are not! My advice, never purchase one. This should never be mass produced because it is responsible for more than 14 fry deaths in my tank overnight. Note the base of the filter, I didn't realize how unsafe it was until I lifted it and found my koi angel fry crushed dead under it. My theory, the filter most likely vibrates up and down from the air pump and the fry have no way to escape. Not even putting panty hose around the base where the slits are or even heavier weighted media solved this problem. I went back to the traditional corner filter with no problems at all. I did contact the person who sold this to me and he refused to give me my money back. I even gave him the benefit of the doubt and ordered a second one, but the problem was the same. Also, it does not keep water clear, not even if you are doing aggressive, CONSTANT (as in daily) water changes. What's funny is, I live in south FL and I ran into another fish fan from completely north FL and he had the same problems with the design of this filter. I give it an F Minus! Don't waste your money on this thing if you care about your fish.