Plecos only would suck on the fish if it was hungry and didn't have much of a food source to go off of. A lot of times that's the case. In my experience with plecos, as long as they are fed enough just like the other fish, they should be fine. For the MBU, I don't have any experience with those. I do have a large African Lungfish though with a big Chocolate Albino pleco and several Common Plecos and two Bichirs. I don't plan on keeping the lungfish or the bichirs in there long because I'm going to make the aquarium into a pleco tank. If you do plan on keeping the pleco with the lungfish, just make sure they both got enough to eat, otherwise the lungfish may attempt to eat it, likewise with the pleco sucking on the lungfish since the lungfish is slow. When I got my lungfish at first, he did try to nip at a few of the fish, but later became more friendly to them. Some have said that they eventually will kill all tank mates that they have, but I haven't had any issues keeping others with him, but I always keep a close eye on them. Like I said, as long as all the fish have a good share of food where they all eat well then there should be no problems. But, since you have a very, VERY nice pleco, you probably shouldn't risk it being with those two.
