Continuous pH problems with soil less mediums-any thoughts?

So heres my issue, and its one that keeps repeating itself. The pH of my soil(less) medium keeps coming out way too low, upper fours, lower fives. This happens straight out of the bag, I dont know why. I've had the same issue from pro mix, sunshine mix, Atami HP, they all start with a low ph. I wonder if my hydro shop guy just has an incredibly old stock or something. anyways, continuing on-
So my ph starts out low, if i flush it untill it runs clear it hovers in the high fives, which is good. However, after a week or ten days the run-off pH is always right back down to upper fours low fives again (reddish orange to use a bush era description). I haven't been hitting the nutes too heavy that it would jump that low that quick, I dont know what it is.
I've tried lots of things. people say put dolomite lime into the mix, which is a pain in the nuts compared to straight from the bag, but i do it. That doesnt help stabalize the ph for very long unless I add around 1 and 1/2 tblsp per gallon of mix. But i have also done side by side studies (fun to use that word) with straight-from-the-bag medium next to dolomite lime and peatmoss/perlite mix. I have found the non dolomite lime mix to veg plants much better for some reason. And as we all know, a properly vegged plant isdamn important. So i dont like putting too much DL into my mix.
Ive flushed and flushed and flushed and flushed with water. That works-for a short time. THen boom, back down again! I cant do that all the time or my plants will never get nutes... Lately what I've taken to is flushing the plants with dolomite lime soaked water, a tbls per gallon of water, water a few gallons through, then flush that with a regular feeding of nutes with extra molasses for the roots (gotta keep those roots happy with some sweets...)
So do you think the rapid pH drops could be from accelerated salt buildup due to underutilization of nutrients due to an initial low ph, or is it that theres something with the medium? I feel like a crazy man like I must be missing something obvious.
I see people talk about how their pro mix, sunshine mix, whatever comes out of the bag at upper 6's....luckyyyyyyy! Am I missing something here?
TO describe my setup, not that its completely relevant to this exact question, but might help.... I grow in both 3 1/2 gallon and 5 gallon pots under six hundred and thousand watt air cooled hoods blah blah, ventillation, circulation, air conditioning, I live in the San Fran Bay area so ....some humidity, but i have a dehumidifier. Temps stay in the low eighties, my tap water is nasty hard, like 8.2, I use cutting edge solutions 3 part series, green fuse bloom accelerant/booster, molasses. I run a drain to waste system....anything else....oh yeah, growing acapulco gold, super lemon haze both the 7 week and 10 week pheno, and xj13. This issue has been happening for a long time, mayve 25 or 30 cubic feet worth of time. Anyways, sorry for the lengthy writting, any help would be appreciated. thanks

are the plants not liking it? my soil ph has always been lower than what people say yet my plants are thriving. respond to the plants, not the meters, especially in soil. just my thoughts, im no expert.

well I have many times had to conteract a burn problem that hits around week five of bloom. Even on my acapulco golds this time I anticipated it. I flushed befor so no buildups of nutes or salts or anything, but the pH still dropped and my plants burned a bit. Since then I have been trying to nurse them back, get some plump in them buds, but try not to burn them any more either..... grrrrr

hey sorry, wow, im fucked up cause i just had surgery today. ive never used "soiless" mixes. I suppose you gotta ph your shit like hydro

no worries, i hope all is well, its good to know that people out there are attentive to others posts.... thanks

Hey Phil - yours is an interesting problem. First off - I wonder if your means of checking PH is accurate. As the majority of all plants utilize a PH in the range of 5.5 - 7.5, just about all soiless mixes ship with a PH around 6.0. It seems like a crazy coincidence that you would keep getting off bags PH'd to 4? Am I to understand you are using the 8.2 tap water? What is the PPM of that water? Are you sure the water source is sound? Have you ever tried using RO water on a test plant to see if your problems go away? You say you are using CE; are you using their PlantAmp product? This product will temporarily lower your PH. Do your plants look salt burned - even though you are underfeeding them? Again, pictures would really help!

hi lionsroor, thanks for the response. I am using the 8.2 tap water (which i would prefer beter but....) but i dont exactly know where to get RO water, it hasnt rained all summer...Basically, no, I'm not certain the water source is sound. But yeah, the plants do look salt burned even though they are being underfed, and none of the lower leafs that would indicate an underfeeding are showing any signs of underfeeding. I am not using the plant amp. As for testing the ph, I use a liquid tester, test nutes in and test the runoff, I can at least guess then the internal medium ph. Not really the best method i guess, and i dont have a ppm reader. But yeah CRAZY COINCIDENCE that all my bags are coming out super low, it makes me feel like I'm takin frickin crazy pills or something. This has happened for certain, to at least the last six bales I have bought! its pissing me off to have to flush 4000 watts of plants every ten days to 2 weeks. I dont have flood tables, only water catching trays for my pots, flushing is a pain in the nuts. Anyways.... do you think flushing with dolomite lime water is a sound enough practice? I have been thinking of "flushin" with michorizal compost teas as I am hoping that might"eat up" all the smaller decaying particles and leave a more sound ph....again though, compost teas are also a nut buster. But then again, I guess you dont get to stay home from work 365 a year and not have to do some pain in the arse stuff.... I dont mind the work, its worth the product, but if theres an easier way without all the extra work, then I'm game!

I've lived in SF and remember the tap water, yuck. Thing is though, with your medium so acidic if you did get r/o water it might make the problem worse.
Ya know those water machines you see outside stores? That's r/o water. I used to bring 5 gallon jugs and fill them each week before I got an r/o system.

The lime mixed with water... might be good idea but how would you measure it?

I suppose if I were in your shoes I would buy a cheap ph pen meter for $20 on ebay.
Get that r/o water, cal-mag and some ph up. Start with half strength nutes and cal-mag then pH to 7.0 and run with it.
BTW Baking soda will raise pH and white vinegar will lower it..

I went out and got a new bale of promix bx, and a bottle of evian or however its spelled water, soaked the promix for 20 minutes,discarded the runoff, squeezed a wad of wet promix, got that runoff and tested the ph, yellow green baby...booyah! Back in business. Gonna go light on the nutes, keep a clean rootzone, and monitor the ph of the runoff. Lets keep our fingers crossed. Thanks guys, I appreciate the attentive help. Lets just hope whats in bloom doesnt react any worse than it already has.

UncleBen!!!! So this is pretty close to my issue only I actually have the stuff to check my pH properly. I am looking to get new base materials. My last run I used a sunshine mix that was primarily peat based. Shitty experience. Potassium deficiency in fan leaves up high like crazy, bad root structure, purpling stems. So here come the Q's. I had like a half bag of the sunshine mix still unused in the bag, tested it's properties and get results of 5.0 pH and 700 ppm(has no nutrient charge). My pots have a consistent reading of 5.5 when i remove soil and test it. Being a organic mix, is it old and breaking down rapidly, is that why its so out of range? Would promix be any different? Vs flushing and trying to rebuffer organic acids between every feed should I feed at a higher pH and let the soil bring down my solution so it still works its way through the pH scale, like 7.0-7.5? Feeding at 5.8 don't sound right 2 me, nor does feeding at 6.4 if your soil is 5.5. What can I buy that is organic, not peat, that I don't gotta put all kinds of shit in, that is 6.5 to 6.8 out the bag with little to no charge?

If u see this and respond thanks for your time, much appreciated

First thing is to get a proper ph meter and see if this problem doesn't go away

Start with a pH pen and see if that gives you a more accurate measurement. Be sure to properly calibrate each day of use.
Color indicator (strips/drops) are not very accurate and are easily misinterpreted.
Update the pH analysis before you start messing with other potential causes.
Make one change at a time.

aisach said:

Start with a pH pen and see if that gives you a more accurate measurement. Be sure to properly calibrate each day of use.
Color indicator (strips/drops) are not very accurate and are easily misinterpreted.
Update the pH analysis before you start messing with other potential causes.
Make one change at a time.

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Meter is properly calibrated. Did a feed and pH adjusted it to 7.5 using liquid lime stone. 2 days later all pots are between 6.4 and 6.7. ec is undee 400, so the plants ate well 2. I am mixing 2 ounces of neutral water and 2 ounces of soil, then immersing my meters in the mix.

Filthy Phil said:

I've tried lots of things. people say put dolomite lime into the mix, which is a pain in the nuts compared to straight from the bag, but i do it. That doesnt help stabalize the ph for very long unless I add around 1 and 1/2 tblsp per gallon of mix. But i have also done side by side studies (fun to use that word) with straight-from-the-bag medium next to dolomite lime and peatmoss/perlite mix. I have found the non dolomite lime mix to veg plants much better for some reason. And as we all know, a properly vegged plant isdamn important. So i dont like putting too much DL into my mix.

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Phil - I use about a Tablespoon of DL to approx. 12 cups soil mix (media, perlite, worm poo, etc). So I think you are on the right track there if you have hard tap water.

I have never checked my runoff ph.... just sayin...

when i reused some peat moss i had similar potassium deficiencies and ph issues... sounds like you have some old peat moss...


I would either xplant or finish off the plant... better to just finish with a potassium deficiency and take a hit to the yield rather than accidentally killing the plant trying to fix this problem.


my suggestions would be to start with new soil from a new supplier next round. I personally like coco because don't run into issues like this. In fact coco can even be reused multiple times if there aren't tons of dead roots in it.

BeastGrow said:

I have never checked my runoff ph.... just sayin...

when i reused some peat moss i had similar potassium deficiencies and ph issues... sounds like you have some old peat moss...


I would either xplant or finish off the plant... better to just finish with a potassium deficiency and take a hit to the yield rather than accidentally killing the plant trying to fix this problem.


my suggestions would be to start with new soil from a new supplier next round. I personally like coco because don't run into issues like this. In fact coco can even be reused multiple times if there aren't tons of dead roots in it.

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Bought soil from nectar for the gods. NFTG #4

Designed for the Nectar line. No bark, compost or wood products. Washed and buffered coir fiber with oregon rain water and limestone. Low EC and the pH should be in the high 6's when you start. Treat it like any other soil you are used to, like FF Ocean, or roots or black gold. It loves compost teas as an inoculant. Hope you like it. Here are the ingredients


- Washed Coir Fiber
- Peat Moss
- Perlite
- Yucca
- Pumice
- Diatoms
- Alaskan Humus
- Worm Castings
- Feather Meal
- Fish Meal
- Kelp Meal
- Paramagnetic Rock
- Limestone
- Rock Dust (Excellerite)
- Mycorrhizae Fungi (Xtreme Gardening) - And a lot of BONE meal!