I know this sounds like an odd question, but to me, it would be useful to figure this out, so I'm throwing this out there to see if it bounces off anyone. I would like to know if there is a relatively simple way to cause calcification of a sheet of knitting canvas. The material in question is Darice #7 mesh (LLDPE), which you can get at any fabric store or wally world. My reasoning for wanting this is related to an aquarium filtration system, mainly used in reef aquariums, that grows algae on a substrate for purposes of nutrient reduction. Right now, the standby material is the #7 canvas, which is vigorously roughed up with a hole saw or saw blade so that it is really prickly. The idea being that this 1) reduces the smoothness of the surface of the canvas, allowing algae to adhere faster and 2) gives a greater surface area for the algae to anchor on to. But in my experience, the thing that causes algae to really get a foothold is calcification of the screen. This happens over time, so I purport that initially, the roughing-up will probably help algae adhere, but if over time this matters less and less, because as calcium adheres to the screen, this creates a microscopically rough surface that, even if disturbed from scraping off algae or scrubbing with a stiff brush, will allow for rapid regrowth of algae. For reference, the algae is removed from the growth substrate on a regular basis (7-14 days). My goal is to figure out how to start with a calcified screen so that I don't have to wait 2 months for that to happen naturally. I'm thinking that I could just take a wire brush to scuff up the material and get rid of the smooth surface, then place the screen in something for a period of time that would cause the calcium to deposit on to the screen. I'm also assuming that it is calcification that is the key here. I haven't had a "mature" growth substrate analyzed or anything, it just seems to make sense. Also I'm not opposed to using another material for the substrate, but it's gotta be "reef safe" material.