"As in some other reviewers, I had trouble with the fry getting out through the sides. 1.)So before the one female would give birth again I put a double folded (the size of the side folded over again), bridal lace over the insides of the breeder tank. 2.)Then I sewed the bottoms to the breeder tank, and hung of the other ends, and put rubber bands over the sides- so they could all stay in place (where rubber bands couldn't reach, that is where the thread came in). I even put a much finer materal on the insides to keep the fry from going through the holes of the bridal material. If you have trouble with this product then try to experiment with material like I did, you'll find this product to work for you even through it's flaws. Yes, the fry get out or eaten by the mother when the fry swim up but that is life. I have guppies that breed and have babies alot, so when I lose some I will have others. I would recommend this product to everyone, with additional information to keep fry from getting out and getting eaten."