Yes, clown loaches are happiest in larger groups (6 or so). Another fine snailer is the YoYo Loach. They seem to be happy in groups as small as 3 YoYo loaches. The Clowns or the YoYos will also appreciate a cave of some sort to hang out in.
I've got 3 YoYos in with several smaller (and larger) species - including SAEs and Coreys. The YoYos seem to mind their own business (eating snails and sniffing around for other food) and leave the other fish and the plants alone.
The only word of caution is that the loaches have sharp barbs like a catfish and can stab the heck out of an agressive fish that decides it wants to bully the Loaches or try for a Loach-lunch. They will defend themselves but don't seem to be interested in starting a fight.
The other thing that will freak you out is that these fish sometimes "play dead" as part of their normal behavior. They can be found sometimes lying on their sides or even upside down. You can look closely and see that the gills are still working. In a little while, they're back up and swimming normally. It's kind of scary at first but you get used to it.
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