maybe the reason you loose so many fry is the way you do your wc, no offense but why do you do "mega" wc and scrubs? really all you need to do is graval vac 25% of the water once a week, and scrub algae off but if you scrub the whole tank and mega clean ...you could be killing tons of bacteria which could explain why you are loosing fry almost right after your cleaning..you dont even need to clean filter material...unless it has a lot of gunk...and then all you do is gently swirl it around in your aquarium water and dont squeeze out too much media...bc again this dislodges the bacteria