Rising Ph

[Guest budz2u]

Hey all, just wondering why my PH is rising so much everyday, from about 5.5 to 6.0-6.2 within 12hrs. I don't let it get higher than this, (it wants to) but i seem to be adding a lot of ph down to keep it under control. Did a flush and water change a few days ago. I could possibly be overwatering, timers 30min on/off because i've got some slight leaf curl on the higher leaves but this may be because of the PH. Any ideas? It's a hybrid aero/nft sytem with 2 seperate rezzys and both are rising. 1st week of flower. Thanks

Grow Hard

[Luke Skywalker]

Most nutrient solutions will be rising at a regular and usually slow rate over time, as the plants take the acidic nutrients from the solution, it naturally becomes alkaline...

 

But if it's rising by that much within 12 hours, there may be other factors at work. The plants may be growing extremely fast, and the reserviour may be too small? A larger reservoir, and therefore larger nutrient solution total volume, will resist changes to ec and ph better than a smaller one. That could be part of it. But you say you have individual reservoirs for the two plants.

 

Some local town water supplies are treated with large amounts of chlorine, which in turn can significantly alter the pH of the nutrient solution, both in initial readings and then as it dissolves out in the air rising the pH levels that way as well. You can avoid this, as well as the purported damage that chlorine can cause to plants, (I've never really had a problem with it, and I use monochloramine (pythoff) in my system in between res changes and crop changes...) by having a large reservoir which the water is allowed to stand for 24 hours with an open lid to get the chlorine to dissolve out. That could help as well.

 

Your flush may have had something to do with it as well, did you flush out the system with ph adjusted water? IMHO all flushing waters should be with ph adjusted water to ensure that no precipitates of excess salts are made in the change from low to high ph that it can cause, and it can also "set" the ph level of particular medias, those with a high CEC (cation exchange capacity)are usually more able to resist this change than those with a low CEC. So if you're using perlite or hydrotron, or growwool in any significant amounts, all of which have a low CEC, like 0 in perlites case, then you may have inadvertantly "set" the pH of the media up at a higher level during the flush.

 

The solution there is simple, just flush again, with ph adjusted water and regularly test the runoff until it reaches the pH levels desired. You'll want to be down around 5.5 or so, but I think you already know that.

 

What's a hybrid nft/aero system? Have you considered that the system itself may be to blame for excessive pH rises? Just a thought...

 

And then theres also the potential issue of overwatering, it's usually advised that nft and aero systems are consistently running a flow of nutrient solution to the plants root system, both to ensure good nutrition and water uptake, but without a constant flow the plants can also starve for oxygen and in aero, particularly, it can mean fast plant death without a reserve nutrient supply. You may have sorted these issues out, I'm not sure, but it could be something to do with it.

 

Oh, and I just thought of something, have you been topping up the recirculated nutrient solution with ph adjusted fresh water? If not the plants may well be taking out significant amounts of water and nutrients, likely a lot more water than nutes, and this could be changing the pH so significantly. Usually its a drop in pH as the water level drops and ec consequently rises, but depending on the plants stages, use of water, conditions they're in etc, it could be a significant rise as well I suppose.

 

A great way to ensure you have a constant nutrient solution level is with a secondary "feeder" reservoir which feeds fresh, ph adjusted and oxygenated (with an airstone) water to the nutrient reservoir via a float valve. It automatically tops up the nutrient tank when the levels drop below a certain point, and only requires a tank to be raised above the level of the nutrient res, which is usually the lowest point in a system anyway.

 

Hope that helps mate.

[Guest budz2u]

:reallyexcited: Wow first up man thanks for the quick and detailed response. I'm really blown away by your effort you're a champion! :thumbsup You've certainly raised some great points and it's given me much to think about.

Rezzys are 40l, it should be big enough even feeding 4 plants not 1! Forget to mention that. I top them up every 2nd day with ph and nute adjusted water, a bit of h202 and superthrive once a week although that's stopping next week. I don't use ST after the 2nd week of flower. not sure about a feeder tank :scratchin

I'm starting to worry about the bottled water I use, it comes in 5gallon bottles PH 7 - 7.2 EC 0. I think the water is too filtered as I've already had mg probs, fixed that with epsom. I'd love to test this shit or at least find out how they filter it etc not possible where I am at. Do you think I should let this water stand before using it. Tap water is off the richter scale, can't use it. The flush was adjusted and I use clays balls and rockwool, both are kosher.

Aero/Nft Aero/Dwc are non "pure" aero systems in which basically the roots are not only suspended in air but also rest in a little or a lot of water. I was aiming for aero but the roots have gotten so big they are now filling the bottom of the tub lying in about a 1cm of water. System has a gravity drain which is quick the water flow/transfer is great! But with the roots getting bigger and trapping water and the pump on less now 30/30 was 45on/15off....... Well im fucking confused now! have to sleep on it i've typed too much and I need a cone. cheers again

grow hard

[F420]

IMO use tap water. it contains minor trace elements that the plants need to survive. Most nutrient manufacturers dont inculde the simple things like chlorine etc that are required by the plant.

Like luke said too much chlorine and you may have problems, but not enough will also give you problems.

Theres a heap of other minor elements also that nutes dont have in them.

 

I would not stop the h202, but I would stop the superthrive. You only need superthrive for early stages and when the plant is stressed.

[Luke Skywalker]

What's the ec of the water?

 

And yeah, using bottled or RO water can cause nutrient deficiencies unless you have a very complete nutrient designed for use with RO or "soft" water.

[Guest budz2u]

I wish I could use tap water but i'm not in OZ and even the locals don't drink the shit here. tap water flucutates between 14-18 EC and 8+ Ph WTF! I've read Using canna nutes which are designed for tap water might not be best idea :scratchin . EC now is 14 it was up to 18 before I switched the lights but since then I've had to back off a bit. I've done 2 smaller grows here already in Aero/Dwc and I had lots of probs as well but still got a decent result. Ahhh the rollercoaster of growing .

here's a few pics of my last closet grow. The strain is Blue Pearl a silver pearl x blue haze.

[Guest budz2u]

pic

[jackfrost]

Hey bro,

 

 

PH can also got up if you have a lot of dying organic material flowing through your water.

 

Try 1min on and 4 off for your water pump, and also air-rate your resi full on. Aero units can have probs with root rot at 30/30 on/off watering times.

 

Also make sure your your water temps are 19 degress with a aero unit, another common prob with aero, people running resi at 25-27 degress, again will cause root rot.

 

Jack

 

 

Ps. I dont think its your bottled water because I used ro/di water with canna nutes before without ph probs.

[jackfrost]

Hey bro,

 

 

PH can also got up if you have a lot of dying organic material flowing through your water.

 

Try 1min on and 4 off for your water pump, and also air-rate your resi full on. Aero units can have probs with root rot at 30/30 on/off watering times.

 

Also make sure your your water temps are 19 degress with a aero unit, another common prob with aero, people running resi at 25-27 degress, again will cause root rot.

 

Jack

 

 

Ps. I dont think its your bottled water because I used ro/di water with canna nutes before without ph probs.

[Guest budz2u]

Hey jackfrost, thanks for the info. I've only got timers that are adjustable in 15min units? What do you recommend? My Ph seems to levelled out now but the leaves are still a little funky.