Thats a Gobioides broussonettii, a brackish fish which wont survive long in a freshwater tank. They are also filter feeders that need regular feedings of tiny foods such as daphnia (water fleas) and freshly hatched brine shrimp.
I think I know what im going to do with it!
Ok im going to take my betta out of his 5gal and put the betta in the 3gal so i can put the eel in there.
Its got a heater and hideouts. Ive also got the right food for him bloodworms freeze dried.
Is that better?
No that wont be ok and you know it! You need to read through what has been said in your thread in the tropical chit chat section. People are giving you this advice for the health of the fish not to have a go at you!