How long do i keep the swordtail fry separated in the breeding net?

They need to be kept separated from other fish until they are too large to be eaten. You also may need to keep the basic rule in mind too. The basic rules for keeping fish successfully are :- 1 inch of fish needs at least 1 gallon of water. :- Every tank needs a permanently running cycled filter. :- Every tank need at least 50% of its water replaced every week.. If you follow the above rules your fish will stand a chance of surviving. If you fail in any of them I can guarantee that your fish will be constantly getting sick.