I have a yellow head moray eel that's about 2 1/2 feet. Regardless of how often you keep him fed, there is no way to rule out that he won't eat the other fish in your tank...or even take bites out of it.
Looking at the fish you currently have, he will make a quick meal out them in no time.
These eels are aggressive and will eat anything that will fit into their mouth and even if it is too large, it will eat it bite by bite(not all fish mind you). I just lost a Radiata Lionfish that was almost 10inches in size to the eel....went right up behind the lion and bit him in half..ate the tail end and then came back for more...was horrible...he twisted in knots just tearing chunks out of the lion fish...he got stung, but that didn't even phase him one bit!
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I've heard of other people keeping these eels with large butterflyfish, surgeon fish, groupers etc. I would not keep lions with them though as they have been known to just kill them for no reason...I found this out a little too late
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I would say your clown would be a quick meal and then the lion stands a chance of being picked on as well since they're still smaller...since you may be getting the eel at a smaller size it may be okay with what you have right now, but not for long.
Whatever you decide on doing, definitely be careful and think about it
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) Good luck!