'Went to do a weekly res. change today in my F&D system & learned a very valuable lesson: Keeping things clean & sanitised is just as important as when brewing.
The res. had developed pale yellow floaty sludge that was blocking the pump inlets. I was too shocked & embarrassed to take/post a photo of that.
After a physical clean (dismantled all the pump components & scrubbed them with a toothbrush), I dumped the pumps, tubing & inlet air filter into a bucket of hot tap water with Sodium Percarbonate & turned the pumps on. After 15 minutes, the water looked like this:
View attachment 4852590
Absolutely putrid! Goes to show you that it's the stuff you can't see that does the damage.
The plants have been drinking/transpiring, but the EC hasn't changed in the res. over the past few days (pH increased slightly). They were basically in stasis.
I've also given the res. & flood table a good seeing-to with bleach gel cleaner, a thorough rinsing & will now hit them with H2O2 before reassembling & re-filling.
I reckon the fact that the res. hasn't had aeration stones running in the past week (I dropped/broke the ones I had last week & couldn't get replacements until yesterday) is the culprit & developed anaerobic bacteria in the process.
From now on, I'll also be adding a small H2O2 dose to the res. every couple of days to stop this happening again.
GRRRRRR!!!!!!