The Dorado recieves regular ass kickings from the jardini to make sure that it knows its place, i'm not sure that it actually cares though

Generally as long as remember to put a little food in every day they all get along reasonably well.
The fish hiding in the picture with the Hemisorubim is indeed an evil fish, thats the Cephalosilurus species (i'm not sure what it is now, meant to be a nigricauda but at 13" it would have to be the biggest one i've ever heard of) Its a pure beast, even i'm frightened of it
No idea on captive size for the electric eel, not enough people have kept them (i wonder why

) judging by the growth rate i'm guessing something similar to that of silver arowana's so roughly 30", should be fun at that size
I've tried getting close ups of the eel but it gets over excited and zooms all over the tank so they all come out as fast moving grey blurs. One of the most active fish i've ever kept, it rarely stops moving and looking for things to kill, its now zapped all the snails i put in as clean up crew and attacks small pieces of wood if they get moved by the current. Luckily it is so flexible it makes arowanas look like lumps of wood in comparison, i've seen it do a 360 turn in a gap no more than 4" wide so at least its not going to need a 30" wide tank to move in, i'm thinking a 6x2x2 should do it for life as a single fish in a big tank.