The USCG is the United States Coast Guard. The school is just feeders, for my oscars and the gar. The sand is not bad at all for siphoning, just take my time and keep the siphon about 1/2"-1" above it and it pulls all the filth right off and leaves the sand in its place, it's nice because the filth doesn't get down in between the particles nearly as badly as it does with the gravel. I started with gravel and was nervous to do sand but now I wouldn't have it any other way. My RES eats All types of fish food (flake,crisps,sticks,pellets) along with feeders, frozen flounder, mealworms, and a small frozen hopper mouse every now and again.