Bakki showers and cold weather climates

[MikeM]

Sunlight not needed. I cover mine with loose groundcloth to prevent leaves etc falling in. Media exposed to light becomes green-black with algae. Media shaded is a nice soft yellow-brown, indicating bacterial biofilm. Read the article Luke posted on porous media showers in sewage treatment applications. It implicitly raises a question of whether the desired bacterial activity would be inhibited by heavy algae growth on the media. I tend to think some algae is not a big deal, since algal surfaces themselves can become the site of bacterial colonies. Media under the top layer does not become algified.

[Regenmeneer]

In fact, bacteria will do a better job in the dark.

Regenmeneer