Many people keep 4-5 discus in 55 gallon tanks, with proper care that should not be a problem. I would suggest to most importantly, get your discus from a reputable breeder/importer and stay away from LFS discus. Buy the biggest discus you can afford, the bigger they are, the easier they are to keep. Over the past few years, I've had many different kinds of smaller fish in with my discus and what I like best are rummy nose tetras, which school really nicely compared to neons or cardinals, the false julii cories (albino cories tolerate the higher temps as well), and bristlenose plecos. Some sucking algae eating fish do get lazier as they get older and will suck slime coat in the dark at night while the discus are sleeping. A lot of people keep a pair or two of german rams with discus. I have too but will not do it again since the rams get so territorial when spawning. It just messes up a peaceful tank.