glass catfish are pretty fragile, and not unknown to dying for no apparent reason. They must be kept in large groups, or they will sometimes die of stress or go on hunger strikes. I don't see why not in regards to platies and guppies, but make sure your tank is big enough to support a group of 8 4 inch fish. They aren't hard to find and buy, but they can be expensive, usually 4-8 dollars a piece.