Have you tried dumping a full can of fish food in the tank, then letting the filter clog? My little sister does that at least once a year.
Are you talking about the thin stuff that grows all over grass, or the puffy stuff that grows on decaying plants? Like at the pet store.
20Gal. Long (Green-House) and 55Gal. Tall (Primary Tank)
4 Fire-Belly Toads, 2 Fire-Belly Newts,
2 Giant Black Millipedes, 1 Grey Tiger Salamander