So my cousin has a 15 gallon aquarium with a few odds-and-ends fish in there. He's new to the hobby and is learning quickly, but of course had some beginner errors in stocking choices. I believe he's got 2 female swordtails, 2 monk tetras, a platy, and this chinese algae eater which he was ill-advised by a chain store to add. I'll say right up top I don't want to talk about the other stocking choices in this tank. That's not the question I'm asking. The CAE is about 3-4 inches long and has been living well with everyone for about 6 months. My cousin now knows about the risks and is monitoring closely for changes in its behaviour, but at the moment it's doing very well. What are the first signs of trouble with these guys, and at about what age/size do they turn from cool buddies to terrors?