I started out with 'colored gravel', but now I'm ready to do it right! I think I'd like to put a sand subtrate on the bottom of my tank for my Oscars. Good idea I read there is a better way than using too large of pea-sized gravel, and I'd like to do the right thing by my fish. Also, a question about just how deep should it be; 2, maybe 3 inches? Plan to do something similar to my 125 gallon tank when I get it set up for the Clown Knives. I've read a little about plants, rocks, caves, etc; and plan to do some nice things with my tanks with time... I'm gonna have to remove the 'colored gravel' with a scoop (I guess, LOL), and then put the sand down ...I hope I don't hurt my fish.... Any recommendations about what kinds of sand? Thanks all...