PVC piping under the gravel is great, but they will still try their hardest to find the spot you least expect. When I first got iggy my fire eel, he was tiny, could fit through the gaps in an AR380 lid, now hes nearly ready for the 800 ltr with the 40cm+ birchirs under a year later.
I feed mine on bloodworms, whiteworms, mealworms, guppy fry and brine shrimp, my zebra spiny is eating ox heart and colourbits too. They steal bolivian ram fry in the most interesting of ways, using their tails as a distraction. The most intelligent fish Ive ever seen by a long shot.
Would stick to the half bandeds unless you want a huge eel, although, I could always take on a couple more in the 8ft if they get to big for ya.