.....Is this a red terror and can anyone tell the sex? He/she is about 6 inches long. Also, he/she is alone in a 75 gallon right now. Is that a big enough tank? And can there be tankmates? Thanks for any helpful replies.
Yup Red Terror! Id be going with male but not very skilled here.
You can check if its a true red terror or not by the O on the tail yours ends half way or so a Uros would go from point to point of the tail pretty much.