No the 20 Gallon isn't where the crushed coral is, it's in the 75 gallon. Thanks for your help everyone. One of our rams died and we decided to take all the crushed coral out and put silica sand in there instead. I know some of my fish are schoolers but the tiger barbs and the clown loach school together so hopefully that will be fine, and I really don't want to increase the bio-load any more by getting any more fish.
What do you think will be the least stressful way (for me and for the fish) to change the stubstrate in my 75? I am trying to decide if I should net all the fish out and put them in a big rubbermaid tub with air and a heater while I do it, or if I should just use a net to get all the substrate out while they're still in there. Also, since it's coral, I know it's going to get cloudy as hell. Is there a safe product I can add to get rid of this just so I can see well enough to put the rocks back in there without crushing any fish.
About the common pleco: This wouldn't be my first choice of fish for the aquarium but my girlfriend has had this guy for over ten years and there's no way we can get rid of him. I'm just glad he's in a 75 gallon aquarium now because he lived most of his life in a 20. We've got a sponge and an HOB because I know a big ass pleco and two apple snails are going to poop a lot!
Thanks again everyone.