I have H. littorale (7 of them). You'd have a hard time killing them even if you were trying. Mine have topped out at a little over 6".
They love to cruise, root around and mine like to eat from the hand. Sometimes they mistake my fingers for food when they still smell like it and will mercilessly suck on them until I take it away. So far they haven't proven sensitive to any of the usual medicines/remedies one might use for common ailments in the aquarium.
They're also pretty easy to get spawning too. I'm not equipped for it so I discourage it with high surface flow, but any time I re-do the flow and leave too much of a still area on the surface, my one male (what a lucky guy, he has 6 ladies with him, lol) will start working on a bubble nest.
Their only drawback is that they can be hard to find, because they aren't exactly a pretty fish.