Coco, Blumats, Non-recirc - pH Drifts Up?

Hey guys (and gals),

First coco run here (graduated from a semi-succesful soil run). I am experiencing a continually climbing pH in my non-recirculating reservoir, and could use some advice. I am about 20 days into flower, and some Phosphorous deficiencies are starting to show as a result of the uncontrollable pH.

Some background information:

Grow medium: 50/50 Coco/Perlite mix

Lights: (4) 1000W

Water: Tap, 30ppm TDS, 6.8pH

Feed mechanism: Blumat drip system w/ 5 gal mainreservoir, connected to a 30 gal secondary reservoir. Water level is maintained by a float switch and pump that transfers feed from the 30 gal reservoir to the 5 gal reservoir, which theoretically maintains a constant water pressure level downstream. This system is non-recirculating.

Nutrients: Fox Farms Hydro (strength depends on plant health and weekly recommended feed), Cal-Mag Plus (~7-10ml/gal), Dripclean (0.5ml/gal)

pH Adjustment: General Hydroponics pH Down (Sulfuric Acid), General Hydroponics pH Up (Potassium Hydroxide and Potassium Carbonate)

Metering Device: Blue Lab Guardian TDS/pH/Temperature meter

I am using tap water (TDS reads ~30ppm and 6.8pH) to mix the FF nutes about every week. I am mixing about 30 gal of feed in reservoir, where the Blumats are gravity fed. At the time of mixing, I will vigorously mix the nutrients to the water in the 30 gal reservoir and let it sit for about 2 hours. At this point, the pH will have creeped from the initial by +0.5pH, usually to around 5.0pH, depending on the strength and recommended week of feed. The water does not vary much in terms of temperature, and will sit around 70-73F while the lights are on, depending on how hot the room is running.

If I were to leave this over night, the pH will swing to 6.0pH. Left unattended, the pH will continue to rise and stabilize at 6.5pH around 48 hours after the initial mix. It also seems like the TDS will rise about 10-15% during this time. Any attempts to lower the pH using pH Down to the target of 5.8pH will have a temporary effect for less than 24hrs, and will result in the pH slowly climbing back up to 6.3-6.5pH. I am concerned with the amount of pH down that is required to maintain the target pH. I have gotten to the point where I don't use pH Up at all, as I know it will drift over a given time. I typically fill the main 5 gal reservoir with appropriately adjusted feed so that the plants can have a properly pH'ed feed during time span where the pH in the 30 gal reservoir stabilizes.

I have read that using RO water is the best form of controlling what is going to the plants. Is this the root cause of my continually increasing pH? It seems that with water that is so clean, this would not as big of an issue as it is now. Another idea is that perhaps there are bacterial cultures in the reservoir that are swinging the pH up, but again, this magnitude of fluctuation seems a bit extreme. My final suspicion would be that the FF nutrients are unstable for this application, but that also seems unlikely.

I have only two grows so far, and am open to suggestions/ experienced opinion.

Let me know if I need to clarify further, and thanks for reading!

I gave up on worrying about 5.8 in coco years ago , let it drift is the way to go, my plants are better looking than before seem to love 6.3 or so. now for first time my ph is dropping lol., just using bi-carb. sulphuric down. CANNA COCO.
FLAIRFORM NUTES.
DUTCH MASTER GOLD SILICA. TAP WATER.

I let mine rise to, sounds more underfed with your ratio, but i use canna. Just ph down again if it rises too much, but all mine like 6.0-6.4, 2.5-3ml/l 3 weeks into flower even with the blumat system which I used, before i ditched it.

I have the same setup as you. Blumat- 5 gal main res/30gal secondary. Mine has a timed pump that comes on every hour to fill the main res. Been running these blumats for 3/4 years. These are the nutrients I've ran through the system:
MB KISS
GH 6/9
V+B HD
Canna A & B
V+B Soft/RO
The ph either rises or falls fast on all of them. Pick your poison. Usually can't go longer than 48 hrs without adjusting the ph. It is what it is. I'm using the V+B Soft/RO now. Yours is rising TOO fast. Switch nutrients.

Thanks for all of the replies, the input is much appreciated. It sounds like the nutrient mix will tend to float upwards over time, and that this is a normal thing. I was mostly concerned with the amount of pH Up being used, but it also sounds like I am in the ballpark of usage on that as well. I haven't used a multi-day rez before, and it sounds like this is just a common issue.

stoned40yrs said:

I have the same setup as you. Blumat- 5 gal main res/30gal secondary. Mine has a timed pump that comes on every hour to fill the main res. Been running these blumats for 3/4 years. These are the nutrients I've ran through the system:
MB KISS
GH 6/9
V+B HD
Canna A & B
V+B Soft/RO
The ph either rises or falls fast on all of them. Pick your poison. Usually can't go longer than 48 hrs without adjusting the ph. It is what it is. I'm using the V+B Soft/RO now. Yours is rising TOO fast. Switch nutrients.

Click to expand...

How do you look the Blumats long term? Do you find that they tend to vary in terms of moisture from day to day? I've been chasing them around the past few weeks, and it seems like one or two out of my 18 will dry up a bit every day. I don't mind having to tweak them, but I would have thought that they would be dialed in by now.

Ya I'm always tweaking 1 or 2 of them for running too dry. Someday I'll switch to a different automatic method.
Each nutrient runs different- the V+B goes down in ph each day. Going down is better than rising because you can bring it back up with protekt/agsil etc instead of using a ph up or down. Your foxfarm sounds like it goes out of whack faster than anything I've tried. That V+B Soft/RO probably is the best nutrient on the market. You should give it a try.

I will def take a look at this stuff - how long have you been using it? Sounds pretty simple versus the half dozen foxfarm nutes I have to mix together every feed session.

about 4 months, I run a perpetual. I stopped using Canna one day and started giving same plants V+B Soft/RO. You don't need anything else they sell. Just the V+B and some Epsom salt for extra mag. Use agsil or protekt to raise the ph every few days. V+B Soft/RO kicks ass. Don't order the V+B HD it sucks.

Keld, do you use any airstones in your rez, mixing the rez?
Just wondering.

GR

stoned40yrs said:

I have the same setup as you. Blumat- 5 gal main res/30gal secondary. Mine has a timed pump that comes on every hour to fill the main res. Been running these blumats for 3/4 years. These are the nutrients I've ran through the system:
MB KISS
GH 6/9
V+B HD
Canna A & B
V+B Soft/RO
The ph either rises or falls fast on all of them. Pick your poison. Usually can't go longer than 48 hrs without adjusting the ph. It is what it is. I'm using the V+B Soft/RO now. Yours is rising TOO fast. Switch nutrients.

Click to expand...

Stoned40, got you beat by 12 yrs, been 52 stoned yrs for me.

I like your point "Yours is rising TOO fast. Switch nutrients." That is a good point but can get very expensive.

I have the plants, 25 days from sprout, in veg now but I will be installing the Blumats within the next few weeks.
I am just wondering how the GH 6/9 worked for you. I am using a modified H3ads formula, 4/6 with Cal/Mag and Epsom. Also add Cannazym and MD 90. I get around 550 to 600 ppm. pH to 5.8 to 6.0.
I am wondering how the pH floats with this product.
I make 4 to 5 gallons at a time using RO water, day 1 aerate the water 24 hrs, day 2 mix the nutes early/ph solution, let sit overnight, check pH. It is usually fairly stable but does float a bit.
What are you seeing using the GH nutes. I had planned on using Canna nutes but I have a gallon each of FloraMicro and FloraBloom and need to use this up.
I am seeing a bit a Mag def. with the Critical Kush. It was mainly in the early growth. First two sets of fans, I then began adding the Epsom, did not think it was necessary with Canna Coco. Wrong again, LOL They are showing no further signs at this time.
Any advice would be truly helpful.

Thanks
GR

I have back off using the Cal/Mag. I now use just Epsom and the plants love it. I have begun using the Blumats and they are working well. 10 gallon rez, with about 7 gallons in the rez, will be adding a 2nd rez to fill the main. Going to just put a 10 to 20 gallon secondary rez with a timed pump to keep the main rez at a near constant level.
I am having difficulty keeping the ppm around 500 with the modified H3ad's formula I am using. At 4/6 plus Epsom, Cannazym, SM90, and drip clean i get a ppm of around 650 to 700. I have back off the GH Micro and Bloom, now running at 3/5 plus the others that I add. Have the ppm at about 550. pH of ~ 5.87

GR

Gr866 - I am using the 6/9 and a bit of calmag when and if needed. I set the ph at 5.7 and it will rise to 6.2 over a couple days and then I'll drop it down or leave it for a couple more days. Chasing the Ph is a bitch, as long as its between 5.5-6.3 I leave it. I usually only adjust my rez 1x per week. I mix 35 gals in my rez and it feeds 4 tables, using two pumps.

Don't know if that helps but that's what's been working for me.