Well... Despite some plant worries, I decided to give it a try, and got myself 5 small Severums, about 1.5" big. So far they've been nice to the plants except for one fish, which periodically nibbles on green rotala, but hasn't done any damage yet. I'll see whether it becomes worse with time or when they mature. I have red, green rotala, ludwigia, crypts, anubias and swords, hopefully they won't become a regular meal for Severums.