I'd second the use of the GIMP to replace photoshop. It's free and
does more than I know how to handle.
http://www.gimp.org/
If you are just worried about color balance, you could consider picasa
from google.
Also free but has very limited features.
re: clearing the tank
Why not take the gravel out and wash it really good?
Thanks for the picture of the cat scan.
/-----------------------------------------------------------------------
/ This is the discussion list of the North American Native Fishes
/ Association (NANFA). Comments made on this list do not necessarily
/ reflect the beliefs or goals of NANFA. For more information about NANFA,
/ visit http://www.nanfa.org Please make sure all posts to nanfa-l are
/ consistent with the guidelines as per
/ http://www.nanfa.org/guidelines.shtml To subscribe, unsubscribe, or get
/ help, visit the NANFA email list home page and archive at
/ http://www.nanfa.org/email.shtml