There are various products on the market for filter feeders.
I use kent chromamax and phytomax and dt's plankton, with good success (I have a large rock COVERED in the smaller varieties of feathers, as well as several large ones).
Most all LFS
' have those or similar products.
The stuff is a'live culture' I guess. It needs to be refridgerated and added to a certain amount of tank water a few times a week (follow the instructions!).
Growing your own would require a seperate tank and lots of unneccesary work..especially when a bottle of dt's or kent stuff last months on end and can provide proper nutriets for hundreds of gallons of water in that time frame.