Firstly how large are the fry?
Does you tank need cleaning urgently, if not Tetra have brought out a solution called "Easybalance". This solution delays the cleaning process. If all else fails and you must clean the gravel, I suggest you use a syphoning kit designed for that specific purpose. The special syphon has a plastic membrane within a see through plastic canister which is fitted to the tube. The membrane permits debris, like fish excreta to pass through but too small to let fish go through.(depending on the size of the fish)
You could as a cheap method, place a piece of muslin over the end of the tube, wrapped in place with a rubber band and holding the tube between your thumb and forefinger manually sweep the bottom whilst the water is syphoned from behind at the other open end of the tube. Fry will tend to swim away from your hand.
OK Its that time again, to clean the tank. Now, please tell me how to siphon debris out of the tank bottom without siphoning the fry! I really dont think I can catch them in a net to remove them, and the whole situation kept me awake all night. (I really need to get a life, I guess) 
But seriously, I have already lost 4 fish in our 2 months of this hobby. My kids are weary of funerals, as also are we. Dont want to screw up again. Thanks friends! 
