The electric waves are just used to locate one another, etc., it wont be a big deal. I've kept multiple species together; it all depends on their aggression. (I could have been a lot more detailed with that, but I'm feelin a little lazy today, lol, my apologies)
BGK and Clown Knives have been kept together with no problems. Same with BGKs and African Knives. Currently I'm keeping 2 Clown Knives with a Carapo Knife with no problems, which is a big surprise to me actually, lol.