Help, High ph in mini-cubes (pics)

[Crotchtrout]

I have been experiencing problem from the get go with this grow. Soon after transplant my rooted clones started showing deficiencies. I was not sure if it was from over fertilizing or over watering. I let the rockwool mini-cubes dry out and the watered with plain ph adjusted water, did not help. I then thought not enough nutes so I watered with a light nutrient (300ppm@.7 conversion). It did not help.

So yesterday I finally flushed with grotek final flush and found a ph problem. I flushed with 4gal. of water to 2gal. of media with a ph of 5.6 and ppm of 100. The runoff form the first gallon of water had a ph of 6.6, ppm of 500 to 550 and was then lowered .2 ph every gallon after that. The final Ph was at 5.8 and a ppm of 100 to 150. I thought that every thing was good now. Today I checked the runoff ph of one of the pots with the same flushing mix and had a runoff ph 7.2.

WTF is causing this? With the second gallon of water flushed there was a slight green tint to the water. I did have some algae growth on top of the rockwool so I added hydroton on top. Would the algae raise ph this much?

I did add EWC tea and some Floralicious plus to my first flood but discontinued use after I noticed some problems. Could there be some biological stuff going on in my rockwool causing ph rise? Should I water with some h2o2 to kill it all and "start over"?

When I first watered I flooded the tray from my res. My res is 22 gallon ppm was 700@.7 with rodi water, maxibloom@ 3.5g/gallon, ph'ed up with silicon (20ml), floralicious plus (2 teaspoon), EWC tea (1 cup) and a ph of 5.7. I only flooded once because of the problems since then I have been top watering by hand.

Even though Grodan says that the mini-cubes don't need to be condition I still soaked them in water with a ph of 5.6 for a few hours. The ph only went up about .2. So i don't think its the rockwool. The hydroton was also washed until the water ran clear.

Stats: 40"x40" grow tent, air cooled 400watt cmh~20" away, 6" windtunnel fan, 2 clip on fans, 3gal. smart pots with about 2 gallons of rockwool mini-cubes, 3'x3' flood and drain table. "true OG" rooted clones from clonville, planted on 7/3. RH average 58% There is a graph of my temps from my controller.

 

[b8man]

Is that mg deficiency? Foliar feeding with some epsom salts wouldn't hurt at that stage, but you're right that it looks like multiple issues which could easily be ph based. Algae wouldn't cause much of a shift....

Were the clay pebbles cleaned before using them? And does it smell of anything (i.e. rotten smell)?

 

[Crotchtrout]

Thanks for the fast reply. Yeah there is defiantly some mg difficinces. I have been foiler feeding some Epsom salt and it has helped. But there are other difficinces like calcium and others.
Hydroton was washed and no rotten smell that I notice. I just don't get why the ph would go up even higher after a flush. By flushing did I strip the buffering ability? It's still has a ppm of 100 to 150 though and 100 ppm is from tap water. So I don't think that's it.

 

[DonJuanMatus]

soak with a 5.4 and start feeding with 5.4......if you are letting your pots dry out too much , start watering more frequently...i have a feeling your fabric pots may not be helping either, i personally would stick to hard sided pots with mini cubes...when you put a small cut in a large pot of wool, it takes a while to have it loose its water, leading to less frequent waterings and ph spikes between waterings...rockwool is spun limestone, limestone is naturally alkaline so it will always want to pull the ph of your ingoing water up..the more frequent you water and the more run off you give, the more stable the wool will be..did you check the ph of the water after you ran it through the hydroton? how often are you watering and till how much runoff?

 

[DonJuanMatus]

another thing...yes algae can effect the reading , as salts get trapped in it...id remove the top layer that has algae, remove the hydroton and lay down circles of black and white poly over the tops..this is what i do and it also stabilizes the temps and humidity in the root zone, similar to mulch in the veggie garden

stay away from EWC and the like, wool is an intert medium and is best used with salt based fertilizers..i would mix a nutrient solution with some h2o2 @6-700 ppms and a ph of 5.4..flush the medium with that and they should turn around..i would also foliar feed them until theyre on track with a calmag solution @250ppms and a ph of 5.8...this will give it nitrogen, mag and cal until the wool is stabilized and the roots can uptake it from the medium

hope that helps

 

[Crotchtrout]

Thanks, that sounds like some good advice. No I did not check ph of hydroton because I just used tap water and I did not think that it was important. My tap water is very hard, 700ppm and 7.4 ph. I have not been watering very much because the pots stay wet, like you said, and I thought I was over watering. Also I had minimum runoff. Now I see that I was probably making the problem worse.

i would mix a nutrient solution with some h2o2 @6-700 ppms and a ph of 5.4..flush the medium with that and they should turn around..i would also foliar feed them until theyre on track with a calmag solution @250ppms and a ph of 5.8...this will give it nitrogen, mag and cal until the wool is stabilized and the roots can uptake it from the medium

I am going to do this tomorrow because Im making my rodi water right now. It takes about 8 hours to make 22 gallons for my reservoir. My plan is too drain and clean my current rez, take my new solution pour it over my plants and flood my tray, let it soak for about 10 min, drain it to my rez., then top it off with plain water, adjust ph back down and adjust ppm as needed. Flood at least every 2 days till plants get bigger, adjust ph after every flood. Does this sound ok? should I drain to waste? I just dont want to have to make all that ro water, it takes about 110 gallons to fill my reservoir
Also how often should I foliar spray the cal-mag?

 

[Crotchtrout]

Ok never mind what I said about my plan. I now found out what you mean about h202@ 600-700ppm. I thought you meant a nutrient solution at 700ppm then add h2o2 to it. I did not know h2o2 was measured with ppm. I found a chart that cleared that up for me.
How many gallons should I flush with? When I did my last flush I had to spread it out over 2 days because my biggest container is a 35 gallon brute trash can with a float valve that fills it up to 22gal for my reservoir. I had to flush 5 plants one day then 4 the next.
I will probably still dump my rez and run the solution to clean the whole system and so the pots can soak in the tray for a little.