They seem to grow really quick... Mine do anyway.
Hint: If you have one of those breeding nets that are stretchy acrylic nets round a plastic frame (rather than clear plastic boxes), check the plastic struts TWICE A DAY EVERY DAY. 2 of my fry managed to swim between the net and the strut and get stuck "round the back". There's a groove running up the outside of the strut, they swum in there, got stuck and carried on growing, getting too large to swim out. Fortunately we spotted them and stretched the net out to free them. THey seem fine, but that was nearly a disaster...
Disclaimer: I AM A NOOB.