Can't speak specifically to yours washing out but I put black sand in my 55 with 3 of the 4 EBJD's I have and their color has darkened significantly. The runt EBJD I have that is in our guppy feeder tank with lighter colored gravel bottom is still pretty washed out. Not sure if the darkening color can be attributed to less stress/stronger fish as I have had them a month and they have been moved around quite a bit. I personally love the look of the black sand especially in contrast to the blue of the EBJD's.