I keep 3 cats together, a Red Tail (about 5") a Tiger Shovelnose, (about 6") and a cat I bought as a Jaguar (about 6"). The Jaguar looks like a cross between the RTC and Shovelnose. I keep them with a few S.Amer. Cichlids, (yes it is crowded) , Anyway sometimes when one of my fish gives my Tiger a hassle, I swear I hear a low growl, Am I trippin or has anyone had a similar experience?