Eel comrades?

I treat my eels with feeder guppies and ghost shrimp. But, normally they are fed with frozen meats. They are nocturnal and tend to only eat when the lights are off. My Arowana loves it all. Feeder Guppies are his treat, and then I also feed him frozen meats as well. As long as it floats, he eats it ;).
 
actually I decided to go with the 75 gallon tank but I will stick to the arowana and eels but what other fish could I put in besides knifefish (with and without knifefish)

thanks
 
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