for a small tank like that, and minnows that is a great, cheap short term solution to keeping some minnows alive.. the problem with this type of system is that you'll get some solids buildup and may have to "vacuum" out the tank occasionally.. by using gravel growbeds, you trap much of the solid waste, i added some red wiggler worms to further break down waste..
i'm using duckweed and anachris(sp??) to keep my a crayfish breeding tank running, and i'll be getting some water lettuce for minnow breeding tank i want to set up..
