I have found that if your system is organic and you are not using gravel or any other medium only water float beds then you can add Grammarus to your sump tank and grow beds and they will eat up all your fish waste. eliminating the need for filters once they establish themselves. They do not harm the plants. You can find them under rocks in creeks and steams.
here are some pictures of them. they are called "Scuds", "water fleas" and "water lice" the last two names are also names of other types of Crustaceans.
go here to read about them
http://en.wikipedia.org/wiki/Gammarus and http://en.wikipedia.org/wiki/Scud_%28animal%29
They do use oxygen so add more air to your grow beds. Also as they grow and shed their skin or die they naturally add calcium to the system and help to maintain a 7.0 pH in your system.
I will add some to my gravel bed system to see how they work in gravel. I hope they will help eliminate the waste in the gravel as that will eliminate the need to clean the gravel.
I am also hoping to add fresh water prawns to our water float beds and see how they do.