I watched a program on the discovery channel a few years back, it was on Fish Tanks and the bloke on there used Rabbit Poo under the pea sized gravel he was using, i can't remember what this did for the plants but his tank was lovely, and he reckons it was down the the Poo!
What do you guys think to this then? i did try it on a 2 footer with just one type of plants (can't remember) the plants did grow well and fast over took the tank to be honest. Not sure what this Poo may do to the water though.