Up until now I have had decent sized fish in my 50 gal that I can see easily while doing water changes and don't have to worry about sucking them up, as they move away anyways. Now as I add more fish and shrimp, I am worried about sucking them up. I have seen where people say to not stick the syphon in the gravel, or put nylon over it, but how are you supposed to vacuum the gravel if you do that? Is it not necessary to vacuum it each time? I typically do to clean any gunk down there while I am doing a PWC. Is it easy to accidently suck a fish up there, or do they tend to stay away or swim away from it? I use a Python by the way.