A couple of weeks ago, I was moving some mbuna juvies around from one tank to another. Mainly, some bigger yellow labs and fuelleborni were going from a 10g to a 40 breeder. They were also in the tank with a dozen rusties, who were staying in the 10g. While netting the others, I inadvertently got one of the rusties and released him into the 40 breeder. Oddly, since then, the rusties in the 10g are double the size of the lone sibling in the 40b. And they were all the same size when the move happened. One idea would be competing for food and the area in which to do it. 40+ fish in a 40 breeder vs. 20 in a 10g. Thoughts?