i have one for my betta. the wire does stick out if you bend it into a different shape. i didn't want it to rust or have my betta get injured, so i took it out, bought some aquarium sealant, put a BUNCH of sealant on the wire (i seriously made sure there wasn't any wire touching the water, haha), then waited about 3 days and put it back in.
my first betta really loved it, he liked to sleep on it at night, and chill on it during the day when he was bored. after he died, i got another betta, and he does the same thing. c: