Hello, I have a 50 gallon stocked with 16 tiger barb. I originally had 10 of the common stripped tiger barb the yellow ones with black stripes with black sand substrate. I thought the substrate was a little boring and everything showed so I went with a fine gravel but my barb literally blend in with the new substrate. I really like the look of the tank so I picked up 6 of the green tiger barb and added them and they look great. Problem is sometimes they all hang at the bottom of the tank. They really didn't do it with the black sand, could it be that they are blending in to feel safer? I have tried different lighting and really doesn't make much of a difference. They are a little more active with brighter lighting but not much. I don't have much flow in the tank and I wonder if this maybe why. My parameters are good and they don't look scared and are eating very well.