Ph problems in dwc

How often do you check pH and is it normal for it to rise overnight​

I am running an aeroponics system with one gallon of distilled water and I have to PH down twice a day. @McLovin777 is running a DWC maybe he can give you some better info on it and @peachfuzz too


Thank you for the help

@B420 I have a 5 gallon DWC bubbler. Some of it depends on your nutrients. I use Rx Green Solutions Grow A & B as-well-as their Bloom A & B. They are low pH nutrients which state not to adjust the pH unless it drops below 3.0 or rises above 6.0. They do an excellent job of buffering the pH and keeping it in the range recommended by the manufacturer. As a result, I have not had to pH my water since I started the nutes 7 weeks ago. :relaxed:

Thank you, always great help here

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Technically this is what is happening

PH drift
In order to reduce the amount of phosphoric acid needed, you need to reduce the pH rise so you do not need to keep lowering your feed pH. This is done by increasing the ammonium content of your feed. Ammonium nitrate solid is banned for sale except if you have a special security licence. It is available in liquid form, but this is at half strength and is relatively expensive.

There is an alternative. This is to add mono ammonium phosphate (MAP) to your mix to give the added amount of ammonium that you need. You are no doubt adding phosphorus in the form of mono potassium phosphate (MKP). In order to keep your phosphate level steady, as you add MAP you reduce the amount of MKP accordingly. Without more detail, I can’t give a definite recommendation for the relative proportions, however about half each MAP and MKP would be in the ballpark, to eliminate your upward pH drift.

Ammonium addition mechanism
How does increasing the ammonium content of the feed reduce upward pH drift?

Two forms of nitrogen (N) are used in hydroponic solutions – nitrate ions (NO3-) negatively charged ions (known as anions) and ammonium ions (NH4+) positively charged ions (known as cations). In soil growing, any ammonium ions present are locked onto the soil particles and converted (the process of ‘nitrification’) to nitrate ions before being taken up by the plants. Thus, in soil, the plant is basically not exposed to free ammonium ions. Contrasting with soil growing, in hydroponic solutions ammonium ions remain available and are taken up very quickly, much faster than nitrate ions.

Especially during the vegetative stage, plants are taking up high proportions of NO3- ions. In order to remain in electrical balance they will be exuding positively charged ions, which raise the pH. If NH4+ ions are introduced into the solution, they are rapidly taken up by the plants. Therefore, the plants compensate by exuding positively charged ions to maintain the electrical balance. These are hydrogen ions, H+, the ‘acid’ ion. Consequently, the pH of the root zone solution will fall.

Therefore, increasing the proportion of ammonium in the feed will result in a relative lowering of the pH of the root zone solution. Reducing the proportion of ammonium in the feed will result in a relative raising of the pH of the root zone solution. This applies to all systems whether recirculating or not. For example, the pH of a recirculating solution may be over 7 even though the feed solution pH has been pulled down to below 6. This is a situation where the use of phosphoric acid to lower the pH will lead to a severe imbalance of high P levels developing in the recirculating solution. Increasing the proportion of ammonium ions in the feed should allow feeding at about pH 6 and to maintain that level with time.

When doing calculations, remember to include the ammonium that comes as part of the calcium nitrate. Typically, about 8% on the nitrogen in calcium nitrate is in the ammonium form, and about 92% in the nitrate form.

@GrowManFitz your nutes may have this MAP stuff in it already. Maybe I will try some. Im tired of PHing 2 times a day.

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The only thing that I can say is , the bigger the res the less fluctuations I have…
When I’m using 5 gallon bubble buckets I really have to keep an eye on my ph… but I usually let it drift quite a bit before I do anything about it… :wink:
When I’m running my rdwc totes everything stays pretty steady , but they hold 20 gallons … :wink:

:v: :sunglasses:


@MAXHeadRoom I won’t pretend that I understood all of that, but I got that I should look to see if my nutrients contain Monoammonium Phosphate (MAP). So I checked the labels and here is what I found.

Grow A
Derived From: Calcium Nitrate and Potassium Nitrate

Grow B
Derived From: Potassium Sulfate, Magnesium Nitrate, Monoammonium Phosphate,
Magnesium Sulfate, Potassium Nitrate, Sodium Molybdate

Bloom A
Derived From: Potassium Nitrate, Calcium Nitrate, Magnesium Nitrate, Dimethyl Sulfone,
Sodium Molybdate

Bloom B
Derived From: Monoammonium Phosphate, Boric Acid, Tri Potassium Citrate,
Magnesium Sulfate, Dimethyl Sulfone, Sodium Molybdate

Ohhhh my man… I only have 10… 10… buckets I PH every single damn day. NO BIGGY! Ha. Honestly I see the only solution as getting an automatic ph adjuster, you can get them for 120 bucks or go blue lab and pay 200 or more. My adjustable flow pump will be here tomorrow hopefully so I can may… just maybe… sort it out so I can just adjust the head… man would that be the happiest day of my grow or what! Totally advise getting an auto ph adjuster if your running loads of buckets in a RDWC or even if you just want a nice easy life where you only check on your plants for entertainment.

Sounds like @MAXHeadRoom is saying the reason I rarely, if ever, have to adjust my pH is because my nutrients contain Monoammonium Phosphate (MAP)… and that is a good thing! :tada: :balloon: :tada: :balloon:

@B420 @peachfuzz @McLovin777

Great info @GrowManFitz I will be going to the Grow store today and pick some up. Looks like it comes in a powder form so I will have to figure out how to mix it. If all else fails I can buy your brand of nutes. Mine do not contain MAP

@GrowManFitz Can you tell me what size bottle you have and what percentage of MAP that your nutes contain. This will give me a starting point for my mixture. :smiley:

Buying some now… hopefully! If this works I’ll be forever grateful to you dudeo

What products do you use? I’ve found a crystal making kit that has it lol nothing else

I’ll post some pics of the labels.

I use the Grow A & B and the Bloom A & B from Rx Green Solutions.

Lots of sound advise here guys love it :slight_smile: @MAXHeadRoom I tend to dumb it down to very simple process as your plants eat they raise ph by taking nutrients that lowered ph out of system a rise in ph is usually hand in hand with a ppm drop. A drop in ph is usually a sign of root stress or too strong nutrient mix and marked by an increase in ppm. Dropping Ph is usually more of a concern it can mean problems no hydro grower wants nute burn root rot pests or general plant stress. Happy plants eat


The PH rise is 0.7 to1.0 points every 12 hours. On 5-26 I lowered PPM from 500 to 390. and added cal/mag. The plants responded favorably to this change. Since 5-26 the PPM has risen very slowly from 390 to 430. A little increase but not much. The plants are dark green and look healthy. The roots are milky white and show no signs of distress. Im doing a test by adding MAP to the solution. I will post results

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lol my ph raised from 5.8 to 7 in last 18hr light cycle ppm dropped nearly 180 from 870 to 700 I adjusted ph to 5.6 added pro-silicate which raised it to 5.8 ppm of 820 should be interesting to see is I get similar ph and ppm drop again Plants are loving the last res change :wink:

Maybe my little experiment can help you out too.

What is pro-sillicate for?