RO H20 + Cal Mag Plus = Unstable pH

[fulltilt]

Hello farmers

having some pH problems. Here's the setup...

20 gallon tote with 6 airstones for a bubbling DWC for seedlings.

Inside the 20 gallon tote there is currently 15 gallons RO H20 w/ 75 mL of Cal Mag Plus (5 mL per gallon Cal Mag Plus). There is nothing else in this reservoir.

Air temps are around 68 degrees farenheit and water temps are between 63 - 68 degrees farenheit.

pH is constantly rising. It needs to be adjusted every 4 hours. This is only a problem when I sleep. If I set it at 5.5 before bed, the next morning it will be in the high 6's.

The mix of only RO H20 and Cal Mag Plus has had 3 days to stabilize in the reservoir although the pH is still steadily rising.

Keep in mind that there is nothing being grown yet, this is a dry run to work any kinks out.

I am racking my brain trying to find a way to stabilize the pH. Please contribute some thoughts to this issue.

Thank You

fulltilt Reviewed by fulltilt on 12-03-2009. RO H20 + Cal Mag Plus = Unstable pH Hello farmers having some pH problems. Here's the setup... 20 gallon tote with 6 airstones for a bubbling DWC for seedlings. Inside the 20 gallon tote there is currently 15 gallons RO H20 w/ 75 mL of Cal Mag Plus (5 mL per gallon Cal Mag Plus). There is nothing else in this reservoir. Air temps are around 68 degrees farenheit and water temps are between 63 - 68 degrees farenheit. Rating: 5

[LOC NAR on probation]

Oh, I like riddles. .................................................. .................................................. .................................................. . Tell us about your air pump lines and stones please.

Humidity in your area has a high PH ?

[fulltilt]

Oh, I like riddles. .................................................. .................................................. .................................................. . Tell us about your air pump lines and stones please.

Humidity in your area has a high PH ?

Hello & thank you for your willingness to help me troubleshoot here...

air pump lines are clear plastic from walmart (have successfully used these before)

two types of stones... 4 from walmart w/ blue plastic bases with airstones set in the top (again have used these w/ success before) and then 2 additional airstones from petco. They are solid stone and black in color.

Does the rise in pH seem out of the ordinary given the circumstances?

thanks

[fulltilt]

Just called Botanicare technical support. They recommended an optimal pH range from 5.5 to 6.2.

They also suggested lowering the concentration of 5 mL/gallon Cal Mag Plus to reduce the rapid pH rises that I am experiencing.

[DreadedHermie]

There's a table floating around on this board somewhere that shows which nutes are absorbed at what pH. (It's different.)

You WANT some drift. High 6's is a bit out of the sweet spot but in my experience, no big deal unless you leave it there.

I had some pH swings in a coco test I did until I added the plants into the experiment. Then everything leveled out.

But if you can knock the pH down to a number you like, and it slowly and predictably swings back up through all the nutrient uptake ranges, that's just about ideal, IMO.

[fulltilt]

Thnx for the response & I'll agree w/ everything you said Hermie, however, my specific problem is that pH is rising too rapidly with nothing but RO water and Cal Mag Plus in the reservoir.

I have just lowered the concentration of Cal Mag Plus to 2.5 ml/gallon at the recommendation of Botanicare tech support and will see if this will stabilize the pH.

On a separate note does anyone know if it's possible to grow a seedling using only RO water with nothing added?

Thanks

[DreadedHermie]

Another thing:

RO water with only CalMag in it has very little "ionic strength" to it. In other words, one drop of pH-up or pH-down will have a profound effect on your readings. There's no chemical buffer there to slow down the swings. Doesn't take much to tip the balance.

Get yourself some nice hard tapwater and A/B it against how your RO is acting with your pH adjustments. Dissolved minerals make the tapwater seem more "stable."

Or, try pH balancing distilled water. :thumbsup: (The less dissolved solids you have, the more wildly your solution will react.) HTH, Hermie

[MerryPrankstr]

Dreaded Hermie speaks the truth here.
I prefer tap water to RO water for my hydro work as it's more stable. I just add my "target" EC to the tap EC for the final EC product.

M.P.

[LOC NAR on probation]

I have to agree with Hermie and manufacture. Put some nutes in the water and watch it stablize. Kind of answers some of my questions about chasing PH. The higher my PPM's with 5 ml's calmag the more stable while light nutes and calmag I'm chasing it down. They put something in the water here so the marines don't go crazy when they come back and it kills plants. LOL

I will try too backing down on the calmag. Might just save a plants life.

[the image reaper]

don't use RO water, pretty much same thing as distilled, no mico-nutrients in it ... keep in mind, just running your airstones, affects pH, as it evaporates acids (alkalis are solid, dont evaporate out) ... as previously stated, the nutes will help balance things out ... but, I ain't no chemist, take my advice with a grain of salt (salt = alkali)