Ive learned alot about keeping fish togethor that you shouldn't in the fresh water game..for example wolf fish. Its always been said one to a tank and never add two different togethor in the same tank. I currently have a 10" columbian black wolf and a generic 14" malabaricus in the same tank..the black in there first..there was a little.bit of agression at first, but plenty of space and lots of food helps greatly. If you remove food agression space issues can be over come.if the tank is large enough. You can keep fish togethor sometimes that shouldnt be. Precautions must be taken though to increase the level.of success. I have a build thread goinf on here currenrly, and i plam on stocking with several.different types of angel fish, which folks always say is a no no. Will see how that goes soon enough and also see if what ive learned with fresh water will apply to salt.Hope this helps if not sorry. Good luck with the eels.