No they can't go in a 30 easily. They get 20 inches long. They don't hardly move. Mine are in a 50 gallon and move all the time. They're just mostly dormant during the day. At night I go in there to feed them and they're zipping all over the tank. Just because they snake shaped doesn't mean you can stuff them in something that small. a thirty gallon is barely one length of the fish. They'll have no room to move around. Please do what's best for them.