The growth of algae, slimes and pathogens is accelerated in nutrient
solutions that are exposed to light.
Further, some brands of chelated trace elements can decompose when exposed
to UV light.
causes them to become unavailable for root up-take.
Light exposure can be minimized by
placing a lid on the nutrient reservoir. Also, cover other regions of the
system where nutrient is exposed to direct light. For example, the top of
open trays and channels.
When placing a lid on the
reservoir, have it in a raised position so that air can freely enter and
exit (Fig 9.5).