RDWC - Res PH tanking after res change

dangler123

New Member
Howdy Folks,

I wanted to see if the community would be able to offer some guidance with an issue that I've been having. Here's my set up:

2 Plant site 3 bucket RDWC, res is external to tent. Total working capacity of the system is about 16 gallons.
Tons of air
400 gph inline pump
260w HLG RSPEC light
General hydroponics nutes using LUCAS formula (1 part micro to 2 parts bloom)
2 ml gallon calmag
2 ml gallon hydroguard
RO water starting at 0 ppm.
Res changes every week
growing Tropicanna banana
44 days into flower

Ph is being monitored by bluelab Guardian ph monitor
A typical reading will look like this: 510 ppm, 71 deg, 5.8 Ph

The problem that i have been having, is that every week when i do the res change, the ph will drop considerably the day following the res change when the lights come on.

For example, i will change the res at about 6pm the night before (lights are on 11am to 11pm) and ph to 5.8. The ph will be fine all night, even until the following morning where it may drop as low as 5.6-5.7. When i check it when i get home from work (around 5pm) the ph will have dropped down to 5.1. I adjust with Ph up to 5.8, it will drop once more to maybe 5.5-5.6 over the following day. Then it is usually good for the rest of the week.

When the Ph is dropping, the PPM remains about the same, may hover up or down about 10 ppm. Water is being consumed about 1.5-2 gallons per day.

Would really love some help in diagnosing this issue. The plants don't seem to exhibit issues indicating any deficiencies or toxicities.

Thank you for anyone who took the time to read this and offer some advice.
 
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MustGro

Well-Known Member
Howdy Folks,

I wanted to see if the community would be able to offer some guidance with an issue that I've been having. Here's my set up:

2 Plant site 3 bucket RDWC, res is external to tent. Total working capacity of the system is about 16 gallons.
Tons of air
400 gph inline pump
260w HLG RSPEC light
General hydroponics nutes using LUCAS formula (1 part micro to 2 parts bloom)
2 ml gallon calmag
2 ml gallon hydroguard
RO water starting at 0 ppm.
Res changes every week
growing Tropicanna banana
44 days into flower

Ph is being monitored by bluelab Guardian ph monitor
A typical reading will look like this: 510 ppm, 71 deg, 5.8 Ph

The problem that i have been having, is that every week when i do the res change, the ph will drop considerably the day following the res change when the lights come on.

For example, i will change the res at about 6pm the night before (lights are on 11am to 11pm) and ph to 5.8. The ph will be fine all night, even until the following morning where it may drop as low as 5.6-5.7. When i check it when i get home from work (around 5pm) the ph will have dropped down to 5.1. I adjust with Ph up to 5.8, it will drop once more to maybe 5.5-5.6 over the following day. Then it is usually good for the rest of the week.

When the Ph is dropping, the PPM remains about the same, may hover up or down about 10 ppm. Water is being consumed about 1.5-2 gallons per day.

Would really love some help in diagnosing this issue. The plants don't seem to exhibit issues indicating any deficiencies or toxicities.

Thank you for anyone who took the time to read this and offer some advice.
I get reservoir PH fluctuations after I mix a tank. The brand of nutes will matter. I just switched to Jacks from the GH FloraNova base and the Jack's has more PH swing with a fresh tank. Water matters. Your super pure RO water won't have any natural carbonates that well water would have, and carbonates buffer PH. Most hydro mediums (like hydroclay) offer no ability to buffer PH and are PH dependent. Soils and sphagnum peat moss based mixes have a high cation exchange capacity and can buffer PH so they swing less. A couple of days of adjusting and I'm pretty good too. Just did my first grow with my guardian; absolutely loved it.
 

myke

Well-Known Member
Takes that long to adjust,try less ph down.Say 6.2 and see if it crashes.Normally it raises, so its the water or nutes buffering as time goes on.
 

dangler123

New Member
Takes that long to adjust,try less ph down.Say 6.2 and see if it crashes.Normally it raises, so its the water or nutes buffering as time goes on.
Hey thanks for the reply! I don't use any ph down at all really. The nutes are naturally pretty acidic. I'll try and mix it higher to anticipate the crash.
 

dangler123

New Member
I get reservoir PH fluctuations after I mix a tank. The brand of nutes will matter. I just switched to Jacks from the GH FloraNova base and the Jack's has more PH swing with a fresh tank. Water matters. Your super pure RO water won't have any natural carbonates that well water would have, and carbonates buffer PH. Most hydro mediums (like hydroclay) offer no ability to buffer PH and are PH dependent. Soils and sphagnum peat moss based mixes have a high cation exchange capacity and can buffer PH so they swing less. A couple of days of adjusting and I'm pretty good too. Just did my first grow with my guardian; absolutely loved it.
Good to know it sounds like more of a normal thing. How frequently do you change your reservoir? And yes, the guardian is dope definitely worth the money. I couldn't really imagine using a pen to check every time at this point.
 

MustGro

Well-Known Member
Good to know it sounds like more of a normal thing. How frequently do you change your reservoir? And yes, the guardian is dope definitely worth the money. I couldn't really imagine using a pen to check every time at this point.
Mostly I swap my reservoir at 7 days; sometimes I'll go to 10. Since I switched to Jack's 3-2-1 my cost for a 30 gallon reservoir dropped to $1.62 Canadian so I swap it more often than I did running the full Gen Hydro line, plants are happier too if that interests you.
 

Wastei

Well-Known Member
Like others mentioned mineral ratios affect pH like I didn't have any pH swing when running Dyna grow but get slight shift for the first 2 days with Jacks. Typical shift is from pH 5.7 to 6.1. I use potassium silicate at 30ppm.
 

dangler123

New Member
Like others mentioned mineral ratios affect pH like I didn't have any pH swing when running Dyna grow but get slight shift for the first 2 days with Jacks. Typical shift is from pH 5.7 to 6.1. I use potassium silicate at 30ppm.
Do you use silica product through your whole grow or just when training?
 

dangler123

New Member
and are you positive you don't have any root rot? that wil cause a pH drop too.
At this point my roots are pretty much un-accessible so I can't be certain I don't have root rot. However, I had the exact same method, strain, nutrients, etc with my previous grow and had the same experience. When I harvested I didn't see any signs of root rot so I don't suspect it.
 

rkymtnman

Well-Known Member
At this point my roots are pretty much un-accessible so I can't be certain I don't have root rot. However, I had the exact same method, strain, nutrients, etc with my previous grow and had the same experience. When I harvested I didn't see any signs of root rot so I don't suspect it.
i've read on here (and it's way above my level of science to understand) that it has something to do with what nutes are being used by the plant during bloom. something about anions and cations and how they relate to the big 3: N, P and K.

i would just set it at 6.1 and let it drop as long as the plants look healthy.
 
and are you positive you don't have any root rot? that wil cause a pH drop too.
My pH always dropped after Res changes in the summer but never winter. And it took my stoned ass several grows to figure out how true the h2o temp is critical to roots. Finally put in a h2o chiller and with this hot ass Colorado summer my roots are white as winter time and my pH with Jacks nutes are stable.....
 

rkymtnman

Well-Known Member
My pH always dropped after Res changes in the summer but never winter. And it took my stoned ass several grows to figure out how true the h2o temp is critical to roots. Finally put in a h2o chiller and with this hot ass Colorado summer my roots are white as winter time and my pH with Jacks nutes are stable.....
great point. i never would have pegged nute temps as a reason for pH drop.
 
At this point my roots are pretty much un-accessible so I can't be certain I don't have root rot. However, I had the exact same method, strain, nutrients, etc with my previous grow and had the same experience. When I harvested I didn't see any signs of root rot so I don't suspect it.
If your not running Beneficials flush your roots with Food grade h2o2. And see if that stops the problem. I had that very same prob and that's what worked for me and led me to understand more about root rot and the effects. You said your temps were around 71, believe me Ive learned the hard way that the 68 degree mark is critical.
 

J232

Well-Known Member
Only thing I found cause ph swing/crash is bacteria and the only quick way to stabilize I found was, 29% or better h2o2, If you use peroxide and it holds the ph, I would be looking for rot or some kinda snot somewhere. I use silica as a ph up and using floranova bloom, there was never a need to ph down. I run the res until I can’t hold the ph or the plants said otherwise. I ran a chiller at 66, light leaks or carelessness will still lead to issues. I’m also tearing the hydro out and going to coco, too much fucking around last run, I’m too old and lazy for that shit, changing my mind daily but that’s today anyways, maybe revisit later.

Will edit and add, air pumps are last resort in my books, air quality fucked me over for a month before I figured that out. What’s your bubblers bubbling in there.
 

smokey0418

Well-Known Member
@dangler123
I have just started getting back into this and over the past months have grasped the concept. Lol
Now looking over very carefully what you are doing an such I would think this.
Your meter if I’m not mistaking reads on a 700 scale so when you say 500 that’s like .7 ec .
I am just starting my second week and I’m just about 1.5 ec , my ppm is 760 on a 500 scale.
I really think you need more nutes in you water to get your ph stable.
Also do the pool shock thing to keep this grow in check then I will add a chiller.
 
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dangler123

New Member
My pH always dropped after Res changes in the summer but never winter. And it took my stoned ass several grows to figure out how true the h2o temp is critical to roots. Finally put in a h2o chiller and with this hot ass Colorado summer my roots are white as winter time and my pH with Jacks nutes are stable.....
Lol I know i really need a chiller, I just don't want to drop the $500+ on it but I know it's inevitable. How did you insulate your buckets/bins?
 

dangler123

New Member
@dangler123
I have just started getting back into this and over the past months have grasped the concept. Lol
Now looking over very carefully what you are doing an such I would think this.
Your meter if I’m not mistaking reads on a 700 scale so when you say 500 that’s like .7 ec .
I am just starting my second week and I’m just about 1.5 ec , my ppm is 760 on a 500 scale.
I really think you need more nutes in you water to get your ph stable.
Also do the pool shock thing to keep this grow in check then I will add a chiller.
The ph meter I have can measure in either the 500 or 700 ppm range and I use the 500 ppm range. Currently about 550
 

dangler123

New Member
Only thing I found cause ph swing/crash is bacteria and the only quick way to stabilize I found was, 29% or better h2o2, If you use peroxide and it holds the ph, I would be looking for rot or some kinda snot somewhere. I use silica as a ph up and using floranova bloom, there was never a need to ph down. I run the res until I can’t hold the ph or the plants said otherwise. I ran a chiller at 66, light leaks or carelessness will still lead to issues. I’m also tearing the hydro out and going to coco, too much fucking around last run, I’m too old and lazy for that shit, changing my mind daily but that’s today anyways, maybe revisit later.

Will edit and add, air pumps are last resort in my books, air quality fucked me over for a month before I figured that out. What’s your bubblers bubbling in there.
So do you use silica through the whole grow?
 
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