i dont have enough stuff to warrant this idea but they sell dry erase boards at walmart etc... take some lumber, a 2x6 would be darn near perfect. stain it, paint it use a router on the edges. generally make it look nice. Then screw it to the dry erase board. Put some dots on your cartos with paint or stickers or something. then get some dry erase markers in the colors of paint you used and write out what flavor is what in the colors you have, matching colors of marker to paint dots on tanks, cartos etc.
you can also buy chalkboard paint and use a piece of plywood and chalk for a unique look.
micro managing, maybe, but still pretty damn organized.