You are correct sir! Nice catch thanks.
5.5 is lower than I usually run my res, but I am going to give that a shot. More room for the pH to swing is fine with me.
I looked at my pH down, GH pH down is citric acid, phosphoric acid and mono ammonia phosphate. Maybe ill look for a straight phosphoric acid one when I am done with this bottle.
Thanks again for your help dizzle. Adjusting the solution pH to 5.6 every day for the last few days has helped a lot, hopefully this next batch of nutes will be more stable though.
NP. Switch out that pH down when you feel like it, the citric acid is definitely part of why you're getting that pH climb. I use
Advanced Nutrients pH down as well, like cctt mentioned. Its ~70% phosphoric acid, its much much more potent that GH's pH down and has a better pH stabilizing effect. Its the only product i have that's from a cannabis-specific nutrient company (e.g. AN, GH, Canna, H&G etc.), i bought a gallon years ago and still use the same damn gallon, almost half way through it by now. BTW i use pure powdered potassium carbonate for my pH up, which AN uses as their pH up as well, but there's is diluted down in water instead of being a pure powder, since the Carbonate/Phosphate buffer combination seems to be the most effective combination at buffering pH, as per the claims of Daniel Fernandez, maker of Hydrobuddy:
Chemical Buffers in Hydroponics : What is the Best, Cheapest Buffer
Daniel Fernandez
...In the end, the conclusion seems to be that in a regular hydroponics system where pH increases generally happen towards the upside it is better to use carbonate as a buffering agent than to use citrate or phosphate although phosphate at its regular concentration in hydroponic does provide some buffering against pH moves (without phosphate increases are much more dramatic). For this reason I believe that a phosphate/carbonate buffer seems to be the best choice for most hydroponic growers, taking care to keep the concentrations at levels that do not cause precipitation or phytotoxicity problems.
http://scienceinhydroponics.com/201...oponics-what-is-the-best-cheapest-buffer.html
Both
Advanced Nutrients and
General Hydroponics formulate their products to take advantage of the phosphate/carbonate buffering effect.
So if i were you, id start off with:
Dropping down to ~5ppm Si to start
Switch to only Phosphoric acid and start pH'ing to 5.5
Add some MAP or DAP to the mix.
That should significantly lessen the issue if not get rid of it. If that doesn't do the trick, drop your pH down to 4.5 with phosphoric acid to get rid of all alkalinity and then raise pH back to ~5.5 with potassium carbonate. This basically wipe out all the 'bad' alkalinity and gives you only 'good' alkalinity while increasing the amount of phosphate/carbonate buffer in your solution. Its an extra step and prolly a pain in the ass, but it will help control pH further if you're still having issues.
