Yes, you need to remove the tropheus. They should be in a group, that stocking is entirely incompatible (it may be young and not causing problems yet but rest assured it will), they require different parameters, and 200L is too small for even a tropheus species tank. I wonder how that ended up happening; it's a very bad LFS
if one sold that fish to them with that set up. Don't know much about bristlenoses, but I believe that is an appropriate tank and community for one, but I believe plecos like that could begin fighting unless the tank is set up well or even no matter what you do ... so you may be better off removing two of them, though if they're full grown and doing well together you're probably good.