Another PH question lol.

I have a couple of questions regarding my nute levels and fluctuating PH. I change my res every 7 days, it is 100 litres. I run a flood and drain style system with the 100 litre tote on the bottom and a 2.5' x 3.5' x 8" deep tote on the top. Water temp is 18-20c and is continuosly flowing 24/7. I use no air and rely on flooming nozzle on pump and water fall effect to lower tote. I use a typical A+B nute mix that is made locally for bottling by numerous name brand companies. So here is what is happening...... Last week I refilled res And added nutes to achieve 775 ppm and added ph down to 6.1 (20 days flower fyi). I typically keep the nutes at 600-650 but was just seeing how they would react. The tds would rise daily by appr 50 ppm and the ph would hold at 6.1 until like day 5 and start to drop, at that point I do add some up to raise it but it typically keeps going down which is when I change water. This week I decided to lower the tds because there was slight browning of tips. Lowered tds to 550-600 ppm and again added down to 6.1. My tds still rose bu appr. 50 ppm per 24 hrs but PH is dropping with in 2 days to 5.8. I added 6ml up and it dropped to 5.6??? so this morning I added 10 ml up and its back to 5.9 but typically with that much up it should be way above 6. So guys and girls whats your thoughts. Algae perhaps? No visible signs but I know it can be hard to spot and I've never had this issue before were PH dropped so soon after change and not able to raise it. I am going to add H020 tonight as well, I haven't used it much this run and in the past added 50ml every few weeks. I will let everyone know if it changes but next res change was supposed to be Monday so may just change it now. Thanks for any insight.

This may or may not be helpful, but i just add my nutes in and let it go. I run a flood table too and i don't even PH it at all and the plants dont seem to give a shit, infact they're happy as fuck.

PPM:1000 @ .5 conversion
Temp: 78 on 67 off
Medium: Hydroton
PH: 6.0 on a fresh res / nutes, around 5.4 when i got like a gallon or two left in the res(i fill it with 14 gallons).

Edit, i use like 6 air stones lol

So you got 100 liters of home brew piss sitting in a tank at 18-20 cel. and you wonder why you Ph floats about on the breeze, look to pumping air thru that 100 liters of decaying OOOZE ..even bugs need 02

vostok said:

So you got 100 liters of home brew piss sitting in a tank at 18-20 cel. and you wonder why you Ph floats about on the breeze, look to pumping air thru that 100 liters of decaying OOOZE ..even bugs need 02

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I dont think O2 is the issue but could be wrong. The water enters the upper res at quite a force, kinda like a water fountain hitting the lid and I would think producing lots of turbulence for oxygen to enter as well as the waterfall effect into the bottom of the res. Not sure what you mean by "home brew piss" could you perhaps clarify. As for temps, do you think its to warm? Like I said I've never had this issue before so don't think its nutes as I've used the same mix for 2 years. PH floating around is not the issue, it drops. but I would think that dropping would mean tds is higher than it should be but not sure if I should lower it more than 550 ppm. I dont want to add air if possible either but can, just a matter of plugging in the pump. It was my understanding that air stones will screw with the PH as well. I will add a couple of tubes tonight and see, I'm changing the res later as well. I did have issues when I did DWC with lack of air and the plants showed it by dropping and the roots turned brown, this is not happening and the plants seem quite happy just curious about the PH as it did stay pretty constant till the 5th or 6th day. God I hope its not bugs, it's a sterile res lol. Thanks for the suggestions guys.

waterdawg said:

PH floating around is not the issue, it drops. but I would think that dropping would mean tds is higher than it should be but not sure if I should lower it more than 550 ppm.

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TDS being too high doesn't necessarily mean pH will drop. 550ppm on its own is sort of low. I understand that your ppm rises over time, but that doesn't necessarily mean your tds is too high. It's just a rule of thumb.

pH fluctuations could be anything, from precipitations to nutrient imbalance. It's possible your plants are just eating the supplied K+ and Ca++ faster than NO3- and H2PO4- since the plant roots replaces K+ with H+ and NO3- and H2PO4- with OH- it would cause the reservoir to slowly become acidic.

When you add the pH up, you're adding potassium hydroxide (KOH), which will add back the K+ and the OH- will steal an H+ and become H2O. You end up feeding the plant potassium. If the problem was Ca++ being eaten too fast, adding KOH to pH up over and over would eventually cause Ca deficiency.

By the way, raw potassium hydroxide is a solid, and sold in flakes. It'd cost less to use that than liquid pH up.

The thing that is strange is the fact that the ph is all of a sudden dropping way faster than it has in the past. The only thing i have changed is the application of kinetin and concentrated K (I think lol) in a foiler feed. I will post the actual product make up but it is called pure flower. I really am not to concerned as the girls are doing very well, just trying to understand. One thing to note as well is that adding HO2O has raised the PH by .1-.2. Thanks for the insight and I will keep reading.

This is the description as per manufacturer.........
"Pure Flowers 0-30-20 liquid was scientifically formulated with cutting edge phosphite technology. Pure Flowers 0-30-20 has the highest nutrient levels ever achieved in a completely solubilized liquid. The unique molecular structure of a phosphite is easily absorbed through the roots and leafs ensuring the crop instantly uptakes potassium and phosphorus. The ultimate flowering supplement will maximize your crop's yield and boost the crop's immune system. The immune system will then be able to better resist powdery mildew, brown rot and other harmful fungi. While protecting, it also accelerates flower development and increases yields. Developed for hydroponics and soilless gardening, Pure Flowers 0-30-20 is super concentrated at 1 teaspoon for 5 gallons."

i did use this last run but not as a foiler spray. Same as the kinetin, but the guy that develops the formulas says it works far better as foiler application. Also pretty sure I had a mag lock out due to high calcium content in water. This I believe has been an ongoing issue but it's takin this long for my newbie mind to grasp. Again thanks for the help.