Yeah, I wish I could get away with changing only a single variable at a time, but the plant is in too bad a shape and its obvious that the algae is/was coming back strongly in the pressurized parts of the system, but I don think I have time to wait.
The way this is going down has me puzzled too. I am glad its working this way, but Im having a hard time seeing what the mechanism is.
Its a complex situation with a lot of unknown variables.
This started with 100% Advanced nutes at EC 1.0
Initially, I completely drained the tank back into the rez before adding the MES and adjusting PH. Then I pumped some of that into the tank and then back to the rez. The idea was to have the entire system - low and hi pressure - starting out with the same exact mix with the MES and all starting at the same PH = 5.5.
Within about two hours, the rez = 5.5, the tank was 5.6 and nozzles at 5.7.
Twelve hours later it was Rez= 5.5 Tank=5.8 Nozzles = 6.0
At that point, it was time to re-fill the rez, but Im about out of ADvanced nutes and I really dont like the stuff floating ont he surface or the apparent precipitation swirling in the water, so I left 3 gallons of that in the rez, and added about 8 gallons of RO and Mega Crop to get back to EC 1.0. I added more MES at 5mM again, and did the PH down, followed by more PH up to increase the amount of phosphorus and potassium in the solution - per @MicroDoser analysis of my deficiencies.
Ive also been adding chlorine every top off for several days - increasing up to about 6PPM.
Over the last several days, the PH difference between the rez, tank, and nozzles has been slowly decreasing.
Dropping the rez PH to 5.2 this last time dropped the PH in the tank AND the nozzles down to 5.5! This is the first time the tank and nozzles have been the same sense my last super heavy chlorine treatment.
I can only assume that the steady doses of chlorine have been slowly reducing the amount of algae in the hi pressure parts of the system. That part I can understand.
What seems odd to me is that in between top off or re-fill, when Im making NO changes to the rez or any other pert of the system, the difference in PH between the rez, tank. and nozzles remains constant. In other words, if the rez was at 5.4 and the tank was at 5.6 and the nozzles at 5.7, they stayed at those exact levels until I changed the PH in the rez. I fully expected the PH to slowly climb in the tank and at the nozzles, but it has not.
It seems to much to expect that I was killing off algae at the exact rate necessary to keep the PH from rising, but I cant think of any thing else.
Twelve hours ago, I dropped the rez to 5.2. When I checked again 6 hours later, the nozzles were at 5.6. Then by 10 AM the nozzles were at 5,5. I decided that was long enough and time to raise the PH back up, so I increased the rez PH to 5.4 from 5.2. A few hours later the tank AND the nozzles are at 5.5 while the rez is still at 5.4.
The algae must be getting killed off - finally - by the steady chlorine.
So, I just now drained the tank again, and raised the rez PH from 5.4 to 5.5. I will check again in an hour or so and see what the tank and nozzles are doing. Im going to need to top off the rez again in another day or two, and Id like to swing the PH up some first.
I will be topping off with straight Mega Crop V2 again, but Im going to lower the MES to 2mM from 5mM. With the signs of the algae being less active, I want to see how the lower concentration does.
Im done with AN nutes.
Almost forgot - there was a film that looked like fine dust on the surface of the water with the AN nutes for the last many days. Plus some signs of precipitaion in the mix. After adding the Mega Crop on the re-fill, that all went away.