I really much depends on the individual fish, and making blanket statements can be misleading. I've kept a couple of SFE's before, one being well over 20 inches long. It was in a tank with two cleaner shrimp for a couple years and it never bothered them at all. The shrimp would hang out on the rock ledge above the eels cave and when the eel came out, they would routinely jump on it and clean it, including inside it's mouth, which the eel tolerated well. I also kept this eel with some clowns and small to medium sized fish and they went unmolested. IME, the real threat to other fish with a SFE is if the fish happens to get too close to the eel when it's trying to snag some food. I fed my eels with a wooden skewer and they learned to feed predictably. As always, your mileage may vary.