but they can be fin-nippers too, so be careful about putting anything with flowing fins in the tank. Keeping tropical fish is all about being aware of the need for all fish to feel secure, and knowing which ones are strongly territorial, and which ones are free swimmers.
Tetras feel safe in a shoal, so make sure you keep them in groups - the more the merrier as far as they're concerned. Angel fish will group together, but they're territorial fish, and they'll defend a spot against all comers - so give them some security by providing cover, they love tall plants .
Assassin snails are attractive, and they won't multiply like other snails - they lay eggs infrequently and in small quantities, and those will be eaten by your fish anyway. Make sure you keep the PH above 7 or your snails' shells will suffer.
Take it very slowly with a community tank, and resist the temptation to keep adding new fish varieties. A biggish shoal of Cardinals and/or neons, plus Angel fish and a few Plecostomus and snails would make a lovely show, and everyone will live happily ever after. If the Angels get really settled they'll breed, and if you see a female studying the sides of the tank very carefully give her a slab of slate, bedded vertically against the back of the tank, with some plant cover nearby. She'll reward you by sticking her eggs to the slate, and fanning them with her fins until they hatch - it's a fascinating process, but watch out for fireworks if another fish comes nosing in.