I have six in my tank and they do a great job of clearing up any flakes from the bottom that my fish leave behind and like it has been said before, they also love bloodworm, not that it is an essential thing for them, or so it seems from my experience. They all seem happy doing their thing in the tank and as long as you go for larger snails, they will live happily with some breeds, as I have three golden apple snails and they swamp the assassins in size, even if all six ganged up on one they wouldn't have a chance (not that I am suggesting for a moment that they are pack hunters!!)