The mudder turned out to be a rather nasty tank mate, a slime eater... its doing it to other carp had been tolerable but it started doing it to the beluga sturgeon, earning itself a one way ticket immediately into a 240 gal for now.
It also behaves as if a filter feeder or something else I have never seen before. During feedings, it swims around in the water column doing very quick lip movements instead of going for the feed on the bottom as everyone else. It's not like our other filter feeders behave, the giant siamese carp and Catla catla as these open their mouths wide gulping as much water as possible with each move. The mudder opens its mouth little if at all, mostly working its lips, the same way when it skims its tank mates sucking their slime off. So IDK what to make of this observation. IDK if it grazes on algae, perhaps it does but I never caught it doing so.
This also may explain its slow growth. I can't imagine it fills itself with such feeding habits in the water column or off tank mates. The tank mates (excluding sturgeon) wouldn't let it suck their slime off for longer than a split second.
It has lost a lot of its attractive coloration in the 240 gal going pale but here are the pictures anyway. It's about a foot long now.
It's peculiar how its tail fin shape resembles that of ATF.