[Delphinus]

You absolutely need a fence like Laurie's or a cover of some kind. Strainers in your overflow are a good idea as well if you use filter socks in at the sump entry point.

They WILL escape at some point. I can't be emphatic enough on this point. You'll have to take steps to ensure that they can't get out of the tank because if the "security hole" is there they will find it. If the worst that can happen is they end up in the overflow that's better than on the floor or stuck in a filter sock getting crushed by the incoming water. Or if there's no filter sock then no worries on the strainers in the overflow since ending up in a sump swimming around is still better than the alternatives. But they will find their way out of your tank sooner or later, you have to make it so they end up not dead when they do.

Other than this point they are a nifty addition and yes Brett they are totally safe with inverts although I would question the safety of shrimp if you ended up getting a shrimp eater like mine (maybe the bigger ones would be safe enough since they can see better than the eel and move faster than the eel, but smaller ones that could be swallowed in a single bite, I'd be nervous). But to give you an example the hermits and hitchhiker xanthids in my tank fear nothing, eel included.

The other potential drawback is the cost versus enjoyment factor. These are well-paid-for fish and if they decide to be social, you're golden, but if they decide to be shy and reclusive, you could end up spending $150-200 on a fish you see at best about 5 minutes per day when they come out for feeding and nary a glimpse otherwise.

So as cool as they are (and don't get me wrong I think they are the coolest little things), they are a carefully measured choice, IMO.

(Sorry to hijack there Laurie..)