I have kept LMB on several different occasions. The smallest tank I ever kept them in was a 55 gallon run of the mill tank. I got them as 1 inchers, and the 3 of them grew to 10 inch fish. I let them go in a stocked pond near my house. I have also had them grow up to 15 inch fish in my 125 gallon tank. I do avoid feeding them goldfish though, I always feed Minnows and then Suckers.
From what i understand the chemicals that we use to take out the chlorine are toxic and from what i understand thats why we cant release our pets into the wild.If someone were to actually eat one you'd end up spending some time in the doctor's office.