You should be fine. I have a 3 incher in my big boy tank and she is doing great. My male was 5" when he went in, and is now pushing 9". He is way down in the pecking order, and is actually quite peaceful and is turning out to be a perfect community addition. I feel that they get a bad rap. But then again I have Devils in there also and they have a bad rep also.Hopefully that grammode does not get eaten. They grow so slow, all your other fish are going to out grow him quickly. If you can keep him safe, he will def be a great looking addition to your tank. Grammodes are mean SOB's though, ill be surprised if you can keep him in your tank without any problems. GL ... Your tank looks great.