I have a Sulfer Head eel full grown 8year old adult of about 22''. He is far to aggressive to have tankmates which I'm ok with but he is holding up in prime real estate right now in a 54 bow all by himself. My question is what would be the smallest tank size I could keep him in with powerful filtration. IMO and experince eels kept alone do not produce a large amount of waste, mostly because they only eat every 3-5 days which is hand tong feed with no leftovers. He also is very lazy as most eels are, holding up in the cave of his choice.