I purchased my green terror 2-3 month ago and he had really vibrant colors but I realized he was losing his color so I thought maybe he needed a tank mate for some reason. I got a the most vibrant Jack Dempsey I have ever seen and he was vibrant for about a week than lost all of his color also. They are both in a 20 gallon tank until next month when my 75 gallon tank gets delivered. The green terror is 2.5”-3” while the Jack Dempsey is 2”. Neither fish is being bullied they both have space to hide. The water permitters are as followed, ph 6.5 nitrate 20 nitrite 0.