I had a 4' one in my first reef. Found it difficult to control nitrates but I had inadequate nutrient export, other large fish and eels, crushed coral substrate, bio-balls. Eventually I lost the battle but the odds were stacked against me. Test nitrates often. They can get away from you fast with this guy in the tank.
No risk at all to fish or inverts. Highly recommend a cleaner shrimp if you don't already have one. Fun to watch it crawl down the eels throat cleaning and come back out unharmed. Mine used to frequent the shrimp's cleaning station and just sit there with it's mouth wide open, patiently waiting his turn.