I just stumbled across this today but I'd like to suggest that you look into south american puffers, they aren't really agressive and will have a great time hunting your snail population to extinction. They are from the same area as most tetras so would make a tankmate that really fits well with what you already have. The clownloach will eat snails but like has been mentioned, he will get way too big for any tank you currently have.
Might I also suggest that you try and PM one of our members called nmonks, he's quite experienced with South American puffers and can tell you anything you need to know about keeping them. By the way they're freshwater not brackish.