iv looked into farming corals in Canada, it would defiantly be a full time job just to adjust your shade cloths in the summer. where i live or a few other places in BC get lots of sun, more then enough to farm corals in greenhouses or to get a really good effect off a sola-tube 75% of the year. surprising a cloudy day is perfect, so even farming corals near the coast is feasible (cheaper to heat your greenhouse in winter). on a cloudy day, no shade cloths are needed, or just a very light mesh. on a sunny day sometime you have to block out half the light. just remember, if its not as dark as night there's light, and some corals grow 10 or more meters under water. when you grow them in a green house in a foot or less it changes how much natural light is needed for different kinds of corals. Anthony Calfo's first coral farm was set up in a greenhouse around Pittsburgh somewhere which gets more snow and less overall hours of sunlight per year then what we do here in kamloops. i wanted a sola-tube reef, but couldn't convince my mom to let me install one
. they do shimmer if you don't use the light diffuser, however that could easily burn your corals on summer days.