I have set up my first tropical fish tank, and currently have 1 Red Tailed Shark, 6 Neon Tetras, 4 Penguin Tetras, and 4 Silver Tip Tetras. The tank is 100l and has been set up for 4 months. I have done all the tests on the water, and it has settled in very well. Ammonia and Nitrate levels are fine. I would like to add a few more fish to brighten up the tank a bit, and I am unsure which fish would be the best to add. I believe I am very limited by the Red Tailed shark as it won't take to many other fish, although, I never see it rarely comes out of a cave type ornament I have. Does anyone have any advice for me?