I have been monitoring some algae development on top of the cubes and some of the nuisance brown algae in the reservoir. I have also noted DO level dropping significantly throughout the week, likely due to organic material in the water stream breaking down.
Although not an critical levels yet, I am anticipating it to get worse. Completely blocking the light from the reservoir does not seem to be an option given the Roto-Grow' design. The cubes are encased in plastic that prevent light penetration to the roots, save the top portion that is exposed to the center lights. I will likely need to either add a UV sterilizer to the intake pump or combat it chemically with an oxidation reagent (H2O2). The UV, while effective, will be indiscriminate on what organic material it will destroy, including any beneficial bacterias. This should not affect the root systems given it will be placed inline with the pump before the flood tray. H2O2 in high concentrations will also have a similar effect, however it will come in direct contact with the root mass. Given the relatively quick conversion to DO, it will likely be best to have the H2O2 added in between the flood cycles so that it has sufficient time to break down before being exposed to the roots. I will continue to monitor for fungus gnats or signs of pathogens and nematodes in the grow medium due to the presence of the algae.
Any hydro experts out there, feel free to weigh in with practical experience in this area.
Picture attached.