I see how you are doing it now. That sounds like a good system you have set up.
I cant remember if I asked this before - how much PH down do you think you add between rez changes?
Im asking because one of the reasons I have been wanting to find a better buffer was to reduce the amount of PH down Im using. As @Northern_Loki has pointed out, adding more phosphoric acid can mess with the phosphorous feed ratios.
Thats one reason I originally switched over to Sulfuric acid. From what I have read, the plants can tolerate excess sulfur pretty well - so the extra sulfuric acid doesnt unbalance the nutes.
But - if you are doing fine adding a lot of phosphoric acid, then maybe thats not as much a worry as I thought.
Yeah, thats the real question - is this PH rise just the nature of the beast with my nutes/water combination OR is it zombie algae related - OR - some of both.
So far, nothing I have done has really made a significant dent in the situation - which tells me I havent gotten to the bottom yet as far as WHY.
The RO water helped a good bit, the chlorine and then the UV helped some, changing to Advanced Nutes helped a lot, but only for a day or so, then its back to normal.
Arguments in favor of infection with algae or some other bacteria, is that adding chlorine did make a difference, and keeping the UV light on is continuing to make a difference. As you said above, there is certainly still some crud in the system that would be a re-infection vector.
The main argument on the other side - that its NOT infection related - is that the Mega Crop, and now the Advanced also, just seems to want to go to 6+ PH even if left in a sealed mason jar.
I started a sample of Advanced Nutes in a mason jar late yesterday. It mixed up at 5.7 PH. Tonight its at 5.9 PH. Thats about the same PH rise I see in the rez over that same time period. The only difference is I add calmag initially in the rez, which makes the starting PH closer to 5.5. After the first 24 hours the rez is usually up to 5.7, so the same .2 rise in PH in a sealed jar as in the rez. Thats after just one day. It looks to me like the Advanced is going to do the same thing the Mega Crop is doing - go up into the low 6's all by itself in a completely sealed system.
So, I have 'evidence' that seems to be pointing to infection, and other 'evidence' that the nutes just do things this way no matter what.
Im going to go ahead and replace the tote and all the plumbing up to the pressure pumps. Thats as far as I can go in a short time. I dont want to leave the roots to dry out. The tank holds enough to run the misters as long as 36 hours or so, but I cant easily replace anything after the pumps without re-doing the plumbing significantly. That will have to wait. That should tell me if there is something in the rez and those pipes causing or contributing to the PH rise. It may only last a day or so, but it will be a good data point.
The Advanced feed chart doesnt distinguish between drain to waste or recirculating - just the one chart. I would assume it assumes recirculating as thats what the majority of folks do.
I got that from an email they sent, but in looking back on it, they were not really clear. Here is what they said when I emailed about buffering.
This is what I got:
New MC formula released last month has improvements in bufferings. Also, the range for Mega Crop is 5.5 - 6.5 pH.
I am sure I found an MSDS somewhere that listed MES as one of their ingredients - but now I cant find it again, so maybe Im mis-remembering? I figured that was the reason they were so $$ was the MES.
The stuff you post on buffering it starting to make more and more sense to me. I think its finally starting to sink in somewhat, because I was able to follow almost all of that fairly easily this time around.
Yeah, so far MES looks like the ticket to me too - but the $$$$ is a killer. Plus - which variation of MES should be used? I have found at least three different ones listed in the buffer calculators on-line. Plain MES (I think the acid form?), MES Sodium Salts, and MES Potassium Salts.
It looks like the plain MES can be used alone or with one of the others? Thats not clear to me yet.
The target PH of the buffer can be adjusted as @Northern_Loki said above. I found a few websites with buffer calculators that allow you to pick which buffers you want to use, then calculate what amounts of the two (strong base/weak acid, etc) to mix together to get your target PH.
and here is the one for MES
There is another one from Sigma Aldrich, but I have not played with it. It lists three different MES buffers, plus a host of others.
BUT - none of these tell you how much is tooooo much for the plants, so Im not sure how useful they will be other than as a guideline for mixing ratios.
Thats a pretty expensive test to do - but Im using the Advanced Nutes PH Perfect Micro, Grow, and Bloom three pack. Three quarts runs around $35
I think I need to pin down what the source of the problem is better - before spending more money on possible solutions.
So far, it looks to me like the natural tendency of both Mega Crop and Advanced nutes (when mixed with my RO water at low EC values - below 1.2mS) is to start around 5.6-5.7 and then rise up to the low 6 PH range within a few hours.
Is that just the way both of them work - or - is my RO water a factor as well. From what I have read, RO does not always remove all the carbonates in the water, so that could be a factor as well. I dont see any way to address that problem though other than buying hundreds of gallons of distilled water for every grow - which is a non-starter.
Add to that that I also seem to have algae crap in the air and water which will re-infect the system on an ongoing basis.
I am hoping that - if - I can clean the system well enough, that the UV light will prevent re-infection long enough to get through a grow cycle. But - thats still gong to leave me with the natural PH rise that either nutes do on their own.
Using MES as a buffer is just going to add too much cost to my grows, so Im stuck using either phosphoric or sulfuric acid. I cant tell if there is any significant difference in how long the PH holds between the two acids. The phosphoric may be a tiny bit better, but that may just be my imagination because the mix I have is stronger than the sulfuric. The sulfuric should be safer as far as phosphorous toxicity goes, but maybe thats not really that much of an issue.