we have some tanks with bottom feeders and some without. Brad still cleans the tanks every week. He will take a "vacum" of sorts and syphon some of the water out while sucking the yuck off the bottom. You'd be amazed at how much nasty stuff comes out of a fish! The bottom feeders won't eat the poop so you should get that out. By the time you do what is called a water change, the poop and food are pretty well mixed together and you can't tell them apart(unless you have monster big fish like we do, then you can tell!
now if we could get them to use an underwater litter box!
Then after brad takes most of the nasty gunk out he will put fresh water back into the tank. It seems to keep the fish quite hardy and healthy. We haven't lost one in a LONG time. Brad is very anal about his fish and if he doesn't know the answer about something, he will look it up and research it until he's postive that is the correct answer.
How big is your tank? Be careful what kind of fish you get so you don't overcrowd the tank when they get bigger. Do you have a filter for it? are you getting gravel or sand? Have you researched the fish you're getting? Some fish can only be fed certain foods. Some can only be fed live foods. If you're getting algae eaters, that's a good start since there will always be something for them to eat after awhile, until then you can get algae pellets that they can eat so they dont' starve.(especially if you just set up the tank recently)
Yes some bottom feeders will eat dead fish. If you have a saltwater tank, sometimes if your fish dies the crabs will eat it and you'll never have to even scoop it out of the tank.(nasty I know but the honest truth.)
Now I am by no means an expert in fish, I just know what Brad knows and we have a friend that works in a fish store so he helps us out when we need help also.