The water temp is 19°c this is the first week I've had them in the tote with water and air. Weak nutrient solution. I can't get hydro guard anymore for some reason I can only get silver bullet which is the same thing. I'll put some of that in. I noticed some light is getting down into the res, very little bit could that be a cause of concern? This area is just where I grow them from seed for three or 4 weeks from seed.
19's fine but at 17.8 K uptake starts to be inhibited.
SIlver Bullet - great name! Go for it.
Light in the res is, per conventional wisdom, a no no so plug the leak. I built a top for my res out of ⅜" HDPE (plastic). I held a flashlight on one side and could see the outline so I sprayed it with black acrylic just to make sure no light came through.
[edit]
I was reading a paper on another topic but decided to check out water temperature vs DO level. Good info
here.
The paper is "Principles of Nutrient and Water Management for Indoor Agriculture" authored by, among others, Bugbee and Fernandez, the latter being the author of HydroBuddy. What stood out was these statements:
"Continuous replenishment of O2 is therefore necessary to maintain about 8 ppm
dissolved O2 (DO) at the root surface. Previous studies have not found a benefit
from elevating O2 in DWC above 8 ppm by using 100% O2 for aeration."
and
"We have used a bubbling flow rate of 5 L of air per minute in a 50 L container.
This high flow rate has been ample even for long-term crops with dense root
growth. Lower airflow rates may be adequate for smaller, shorter-term crops."
The latter paragraph is the only metric I've seen for the size of the air pump in a hydro res.