This is more related to my african cichlid tank, but still could apply to planted tanks. Are there any "easy to find" true detrivores for freshwater aquariums? I've read earthworms,and yes I realize my african's will eat them.
A close "cousin" the black worm (Lumbriculus Variegatus), not Tubifex could be a good source. but these too will become food over time and generally breed too slowly to have a going culture in your tank with fish; or any tank for that matter as long as you are useing them for a food source.
Other Detrivores are Ostracods, daphnia, rotifers, ceriodaphnia, copepods, amphipods, and yes tubifex worms. These can be purchaced as cultures from certain sources so they will be safe for your fish and tank over all; however, these too will become food for just about any and all fish. If the fish can get the food in its mouth its gone.