if you want to suck up muck from the bottom, I use a large syringe with a bit of irrigation tubing on the end to suck that up, haven't sucked up a fry yet!
and for just normal water changes I use a white measuring cup (the ones used for baking) and just gently scoop water from the top of the tank, if any fry get scooped up they are visible against the white of the cup.
we use a smaller tank for the breeding so water changes are quicker and easier than in a large tank.
a bit time consuming but its worth it to see them grow up nice and healthy.