I don't see where anyone was rude, I've seen repetition due to the OP being a little stubborn. It seems to be of late that a lot of people are complaining about people being rude when ever their own opinion is challenged. People need to stop being so sensitive and realize a difference of opinion isn't an insult. It's merely someone trying to empart their wisdom(though I'll admit some people's wisdom is questionable at best). Ahhh, I remember the good old days when they're actually was a real reason to complain. Insults to people's intelligence, financial resources, personal insults, flaming etc....
I have seen some bad advice in this thread, best advice in my opinion came from Oddball. RTC are predators get ridiculously large and though they'll eat anything they don't sift the sand for small food particles and such. So they shouldn't be ever considered for a clean up crew, they're just another mess to clean up after. Bichirs as well are predators and aren't given to sifting so again wouldn't be clean up crew material. They're looking for something substantial and will over look the small debris a clean up crew is supposed to clean. At best occasionally barely ever they'll bury themselves which could possibly toss debris into the water column. Again they're just another mouth to feed and to clean up after, not beneficial to cleaning. Stingrays do toss up the substrate but as was said they're a fish you build around not a after thought to merely clean the tank. If you expect them to live on scraps you'll quickly wind up with a dead stingray.
As I said best advice came from Oddball, Geo's are a good clean up crew as well as large Cory's, Hoplo cat's and loaches. That's not to belittle them or the consideration necessary to maintain them. It's just that they can serve a beneficial purpose to helping maintain the tank. Geos, Cory's, Hoplo's and loaches sift substrate constantly and will sort out small food particles and consume them as well as turning over the substrate helping to toss debris into the water column and help give your filtration the opportunity to filter it. They also help maintain the look of your tank if your using sand by turning over the sand and helping stop the growth of algae on the sand particles.
It's a hard think to do, but the most important thing an aquarist can do to keep a successful tank is to be able to compromise. There are plenty of fish I'd love to have, but I choose not to keep because I can't maintain them properly. I love stingrays and have kept them in the past, but I now know I shouldn't due to my tank size. I love Silver Aro's again don't keep them because I can't maintain them long term. I try to choose compatible tankmates that compliment each other visually as well as personality while compromising where ever it's necessary. That's my opinion at least.