Oh boy that thing is a perfect ray tank. Yeah good luck on moving it in the basement, at least it is not glass. I see more rays in your future and do not play like you won't buy more. You will put all your rays in that big tank and the first thing you will say is "man this thing looks empty"
As far as the bottom try to match a color whether it be tan or gray to match the color of the sand you are putting in the tank. That way when the rays push the sand around the bottom is atleast the same color. You could even do a speckled look. Get a spray can of the darker color in the sand and mist the bottom of the tank then paint it with a latex or a heavy coat of spray paint of the lighter color to mimic the sand look. Just a thought
As far as the bottom try to match a color whether it be tan or gray to match the color of the sand you are putting in the tank. That way when the rays push the sand around the bottom is atleast the same color. You could even do a speckled look. Get a spray can of the darker color in the sand and mist the bottom of the tank then paint it with a latex or a heavy coat of spray paint of the lighter color to mimic the sand look. Just a thought