my eel is about 7 yrs old right now he went from 4 inchs to about 15 inchs in about a yr or so after thaat it was very slow growin. i have mine in a smaller tank also but when i had to keep a veija bifactious for a friend it was a war all night long so the biffa didnt stay long. honestly a 125 might be a decent home considering the average kid will put it in a 20 gallon