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As promised here are some pics on how I grow biofilm at work. We use polycarbonate sheets, a material used in abalone aquaculture for biofilm culture. Note two things that make it ideal for the purpose 1: massive surface area to volume ratio, 2: clear allows easy viewing of biofilm growth. We use pvc pipe to hold the plates upright (abalone farmers use baskets) to maximise exposure to light and prevent too much sediment from settling on the plates. There are two factors I believe that will greatly improve your biofilm growth. 1. Water flow. Moving water promotes growth on surfaces and slows greenwater growth in freshwater, allowing your biofilm to outcompete it. 2. Nutrients. If biofilm growth is slow, we add fertiliser. Alternatively just use water from yiur aquariums as this is generally quite high in nutrients. This is a single plate: note that on the plate you can see areas that are different to others, indicating different organisms growing on different parts of the plates. The following are pics of scrapings taken from the plates at either 40 or 100 times zoom: Long green things are filamentous algae, brown round things are diatoms Diatoms The grey things in these are stalked ciliates, attached by their stalks, they filter feed using their bulbous heads. Brown stuff is diatoms. Some diatoms and a macroalgae (seaweed) germling. Some more diatoms but notice the chains of bigger diatoms through the middle. These are motile i.e. they move. Crazy. A copepod (centre - grey coloured) found amongst the biofilm. More biofilm with an unidentified 'worm-like' organism Other random shots All of these scrapings came from plates cultured in the same raceway. Now that see can see this complexity, you can understand why one vegetable/food item just can't compare. Utilising my experience with this technique I built my own biofilm plates for growing biofilm for pleco fry. The plates are roughly 200*200mm and 10mm apart. It allows fry in to feed and stops adults from eating everything before the fry. only problem is that the polycarbonate has split (look closely) around the nylon bars. I think I'll move back to using PVC pipe to hold them apart.