Well Mike i actually like it! It is of a round consistency its not gaudy and its small enough for the rays to bury themselves if they feel the need.Rays that have lived in captivity for a long time seldom bury themselves anyway.The other thing i like about this medium\small gravel is that its very practical,it doesn't end up in the filter chambers damaging moving parts in pumps either....i use this grade of gravel on many of my tanks with great success,like iv'e said before so long as it isnt too big and is round smooth and not too deep it works well.
Don't get me wrong i like the sand also,love Alans white sand with the large black pebbles.
Generally hate multicoloured substrates but thats a nice suckle combination of colours in my eyes and your rays look good on it.
Each to their own mate!....so long as the rays aren't suffering that is.