Sam
In photoshop I was able to correct for the blue cast. How does this look
As for the sand being washed out. depending on the camera you are using. If you have the ability to switch metering settings try switching to spot metering. Then meter off something in the tank that is halfway between the white of the sand and the dark of a cave. push the exposure button halfway down then recompose your shot and take the pic. This does not always work but thats what I do.
J