Dave, That's what I was trying to get at with earlier post about water quality. As far as I can tell, the general consensus is "??". There seems to be a lot of rules of thumb and house knowledge, but no real data that I can find. One thing that I've been looking at for a while is a technique called aquaponics that may come close. What you would do is use the aquarium water for a style of hydroponics that is a closed loop and uses fish waste for a food source for the plants. I've been following some of the work being done here: http://www.aquaponics.com/ and have a few of their newsletters that I purchased and could share if anyone is interested. I would love to work with someone on this to do some actual testing and figure out something in a more scientific manner. Jesse _______________________________________________ GSAS-Member mailing list GSAS-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/gsas-member