Adventures in Hydro #2 - LP Aero/NFT mash-up - or - switching to HPA?

Indoor Growing Hydroponics
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543

Got the UV light - and it works! Well, its not broken and it does turn on - two of the main complaints in reviews from similar lights.

The other main problem is leaks. Lots of complaints about that. So I decided to re-seal the cable and end caps with some marine grade sealant. This stuff is considered a semi-permanent repair for saltwater boats, and is UV stable, so should work fine.

About those leaks - I didnt read the fine print until last night. The water resistance rating is IP68 - which is NOT 100% water proof! IP68 means:

Devices backed by an international standard rating of IP68 are deemed fit enough to withstand dust, dirt and sand, and are resistant to submersion up to a maximum depth of 1.5m underwater for up to thirty minutes.

So, no wonder people have leak issues! All the cheap ones I checked had the same rating, but Ive been boating for decades, and the 3M 4200 and 5200 are bullet proof. The 5200 is a step up from 4200 and is considered permanent, but my tube of 5200 is as hard as a brick, so I had to toss it out. :slight_smile:

Forgot the pics!

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After the 4200 sealant cures - 24 hours - I will take the light off the foam and put it in the water. In the mean time, the hi humidity in the rez will help it cure faster.

EDIT: If you are looking to get some 4200 or 5200, be sure to get the FAST CURE version. Fast means 24 hours. The regular or slow cure version takes 7 days!

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544

Cool.

But, interlock that thing. You do not want welder’s burn on your eyeballs.

The root ball is gorgeous!

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545

Yup, I did a lot of arc welding when I was in the service - burned my eyes many times. That comes from being young and dumb and trying to out macho other equally dumb assed idiots :slight_smile:

I dont have a good way to automatically lock out the light when I pull the lid off the rez. Im going to have to remember to turn it off when Im working in there. If I get my eyes burned again, that will probably help me remember :wink:

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546

Lol, tell me about it. If I only could rewind 20 years. Had a few hold my beer moments. Fortunately, Darwin stayed away :sweat_smile:

547

LOL I used to be (more) smug, and tell myself I wasnt as dumb as some of my friends who had serious ‘hold my beer’ moments. Looking back on it now, and tryin gto be more honest, I think I was just luckier :smiley:

It occurs to me that this is a good reason all by itself, to use some sort of shield around the light. I just checked the 4200 sealant and its nice and firm, so I stuck it in the water. Being under tinted water helps with the UV effect on the eyes, but its still not good Im sure.

Gonna go cut a small piece of ABS pipe a bit longer than the light later today. I hope ABS sinks - the light wants to float, and Im not sure I trust the suction cups to hold it down over time.

548

So it seems that after a few days the levels of PH up and PH down that were buffering the solution are depleted and the effect of the H- ions from the roots is dominating too much.

The PH is dropping too fast and this means I have to pump out too much solution and as a result, I will end up using far too much food if I continue.

I will go see them after the weekend and make sure all the buckets are filled and all the lines are clear.

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549

Have you been following the buffer thread?

I Know you’re using different nutes, but the buffering aspect should apply to any nute.

I have to admit I have not been doing my homework on buffers. I need to work on that…

550

Time for an up-date.

Ive been seeing some tip burn and even some on the sides of a few leaves, so I dropped the EC from 1.2ish to 0.9 ish when I topped off the rez. The lower concentration is less stable, or I should say less buffered as far as PH.

There is always about 3-4 gallons left in my rez when the water gets down to the drain pipe, and I only added an additional 5 gallons. After mixing, the PH wanted to stay about 5.7, so I added some PH down, but it dropped to 5.3. I left it there hoping that would offset the rise in the accumulator tank, but it didnt seem to make any difference. Water drawn from the accumulator is still right at 6.0.

There was some chlorine still in the water left in the rez, so this isnt a perfect test, but so far, the rez has not clouded up or had any floating scum with the new UV light. The big test will come on the next re-fill, I dont plan to use any chlorine at all next time. Im hoping to be able to go back to spraying the roots directly with bennies.

Other than the tip burn, the plant still looks good. Its interesting to me the variations between individual branches on the same plant. One of the tallest branches has the smallest buds, and they are further apart than the rest. All of the leaves have some tip burn, but only a few show side burning on the fingers.

Its slowing down, but the roots are STILL growing!! I can no longer reach in to clear the drain of roots without smashing the upper umbrella. I had to move another one of the nozzles up top because it was getting buried - again. Im also going to have to trim the duct tape roots again. Plus, I cant get my hand holding my phone into the back of the chamber any more - there isnt enough room at the top or sides.

This is day 30 of 12/12. Should be the 1/2 way point, so 30 more to go…

551

This is the cellphone dent from two days ago to today.

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552

Not really, I do know that I don’t have enough crap in my solution to keep a stable PH just by adding RO water so today I need to go see them and fill up the bucket of PH up. They will be fine then.

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553

Which PH UP and Down are you using? I am still not at all clear on buffers, but if the ones you are using work as a buffer, I may change over.

The ones Im using do not buffer at all as far as I can tell.

554

Using a PH down, with what is the typical formulation, of phosphoric acid and then adjusting the PH back up with a strong base such as KOH, you are essentially creating a buffer. It may be rather weak around where you want it but none the less, it probably provides some buffering. As such, the formulation of the UP/DOWN may or may not create some buffering as a side effect of your PH adjustment.

Example:
H3PO4 + KOH (phosphoric acid + potassium hydroxide) will produce some equilibrium of KH2PO4 / K2HPO4. This is a phosphate buffer.

By doing this, you have just produced the conjugate acid (KH2PO4, monopotassium phosphate) and the conjugate base (dipotassium phosphate). Adding more KOH will continue to shift the ratio towards the conjugate base (dipotassium phosphate). During this process, the effect on the PH is reduced. It is buffering the PH. This will occur until all of the conjugate acid (monopotassium phosphate) has been depleted (converted to dipotassium phosphate). Any additional KOH added after that point will move the PH quickly basic.

Megacrop already has monopotassium phosphate in the ingredients. This is one of the components that makes the solution weakly acidic. Adding a base to adjust your PH up is, in essence, creating a phosphate buffer as described above.

Reality:
Add more of both in the proper ratios, more buffering capacity at your PH. But, at this same time, you are also adding additional potassium and phosphorus into the solution (using this example). Because of this, there may be concerns of precipitation through side reactions along with phytotoxicity due to the increase of potassium and phosphates. Further, phosphates sequesters calcium and magnesium. So, there is likely a limit to how much you’d want to add.

What buffering is actually being created, though, is unclear since the formulations of the off-the-shelf UP/DOWN may vary from brand to brand. Also, because the solution contains a complex mixture of salts, there are likely a variety of buffers being created. By adding PH UP and DOWN, you’d likely be creating several different buffers or, at least, increasing the buffering capacity of the solution to some extent.

Now, whether a phosphate buffer alone is sufficient will be related to the user’s unique situation and is an entirely different matter.

Side note: In the other thread, the titration of just the MC with KOH illustrates the inherent buffering. A phosphate buffer has pKa values of 2.16, 7.21, and 12.32. You’ll note, the PHs at which buffering is strong (the pKa values), is a distance away from the PH values that are most useful to us. It will weakly buffer against the upside but the strongest effect is at over PH7.
The citrate buffer has pKa values of 3.13, 4.76 and 6.40. Which is closer. The MES has pKa value of 6.15, which is even closer yet.
In all these three examples, we see buffering but the amount of the buffering in the range of usefulness clearly differs.

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555

Round these ways, there is a very limited range of chemicals available. Some are local chain brands, others are Canna etc but the chemicals are the same, just in a different bottle.

I think I am doing this. KOH for sure 100%, and I am pretty sure the PH down is phosphoric acid. I would remember if it was nitric or some other sort.

And this matches my real-world experience. I used to find the solution really liked to stay just over 7 and it was hard to move it away from there but once you had it needed much less acid to produce a greater change.

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556

Thanks for the feedback guys, but…aaarrrggghhh! My brain is mush. The comments from both of you got me back to reading about buffers again, but as usual, I got lost down the rabbit hole.

One site that keeps popping up in my Google searches is this one.

https://scienceinhydroponics.com/2010/08/chemical-buffers-in-hydroponics-what-is-the-best-cheapest-buffer.html

This is the guy who wrote the HydroBuddy software. I have it installed, but have not figured out how to use it yet.

He has a few ways to handle PH swings, but as far as buffers, he suggests that using MES is ideal, but $$$. The next best is carbonates, but I cant figure out what exact carbonates he is talking about.

It sounds like phosphates and potassium are both potentially toxic if too much is used, and citrates just didnt work that well.

From the link above:

The red and yellow curves represent two solutions with increasing levels of carbonate showing us that if you are battling pH increases, having more carbonate will definitely help you deal with this. However it is also clear that carbonate concentrations at pH 5.8 are restricted to around 100 ppm since values above this are bound to cause toxicity due to the very large presence of the hydrogen carbonate ion. The green curve represents an increase in the amount of phosphate from 0.002 to 0.004M (about 100 ppm) with carbonate, showing us that phosphates are not good at buffering increases towards the upper side but they do increase buffering towards acid territory. Overall I also noticed that citrate concentration increases to the maximum threshold allowed by calcium citrate solubility did not afford a very good buffering effect with only a mild effect that prevented shifts towards the downside.

In the end, the conclusion seems to be that in a regular hydroponics system where pH increases generally happen towards the upside it is better to use carbonate as a buffering agent than to use citrate or phosphate although phosphate at its regular concentration in hydroponic does provide some buffering against pH moves (without phosphate increases are much more dramatic). For this reason I believe that a phosphate/carbonate buffer seems to be the best choice for most hydroponic growers, taking care to keep the concentrations at levels that do not cause precipitation or phytotoxicity problems.

BUT - then I read another of his blogs about using ion exchange resins.

This sounded perfect to me. The resins are very $$ to buy, but they can be re-used up to 100k times and are easy to re-fresh - just soak in vinegar and wash. So that brings the daily cost down to a very reasonable level…maybe.

However, finding some in a small quantities is not easy. He says about 1 gm/gallon of water is enough, so I only need 20 gms or less. Ive managed to find some sources, but they either wont sell to me or they are in Europe with 6 month lead times or they are out of stock or the minimum quantity is 200 gms for $500, etc.

The other issue is everything I have found so far is very fine powder - 70-150 uM, so I will need a very fine mesh bag or container if I want to be able to re-use it and not loose it into the system.

So, ion exchange resins might work great, but you cant get them and the particle size is too small to re-cover them easily…

Im still looking though.

He has some other blog posts about mixing nutes so they are somewhat PH stable, but I havent gotten to those yet.

On a related but slightly different topic - the Advanced nutes just cant hold PH for more than 2 days before it starts to go up fast.

The UV light seems to be at least as effective as the chlorine as far as preventing scum and precipitation, but the PH still shoots up after roughly two days and I have to start PHing it back down.

However, I noticed a few days ago, that when I forgot and left my pump running full time, that the PH went up much faster and sooner. I forgot about that until today. So I have changed the re-circulating pump from 1 minute ON and 5 minutes OFF to 1on/30off. So far, it looks like the rate of increase is less when I circulate less, but its too soon to tell for sure.

That seems to say that I also have a carbonate issue - even with the RO water, and that circulating the water is causing the PH to go up due to C02 exchange - I think. Maybe.

Im going to watch this for a few days to see if the PH swing gets better with less circulation.

On the other hand - the plant and the roots still dont seem to give a crap that I am having PH issues. Other than slight signs of tip burn (EC too hi), and some purple on some leaf stems (Mg def?) they look great and are growing just fine.

However, I CARE ABOUT THE PH!!! Stupid plants just dont understand that PH needs to be IN THE CORRECT RANGE or the world will end!!!
:smiley:

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557

AFAIK (and someone correct me if I am wrong) but carbonates are literally dissolved CO2 etc.

This would be an acid of some sort, which could combine with something else to form a buffer.

Whilst CO2 forming carbolic acid would normally be predicted to lower PH, it may be that it is forming a buffer which wants to buffer the solution at a higher PH. My chemistry is not good enough to know whether this is actually the case, or what it would mix with to form a buffer but it seems a possible reason why adding acid would raise PH.

I have suspicions about these ion exchange beads. If they work so well, why have they not been turned into a product yet?

I always use this as one way to see if any new theory or effect is real. If it is, someone will try to make money from it.

Conversely, if they work so well, turn them into a product…

Stupid plants, growing well when the PH is out! Don’t they know they should be looking ill?

I always tell my plants “In this house, we respect the laws of physics and chemistry!”

And they listen and refuse to grow well unless I am bang on target, hehe.

Even now, 2 years into learning RO, I am unable to truly get rid of all nute deficiencies. There is either a potassium or Mg def (similar symptoms, different causes) which is not as bad as it was, but still not as good as I would want. Dipping down to 5.4-5.5 for a day every three days is helping but like your on/off timings needs more experimentation. That said, even with a def I can hit 1.3GPW now on a good run.

If phosphorous had more obvious signs of a def, that would help in diagnosis…

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558

I found this in my “hydro list of links” – maybe there’s something in here that will be useful.

http://microscopy.berkeley.edu/Resources/instruction/buffers.html

Those are pretty interesting. Another rabbit hole for me this weekend! :slight_smile:

The original blog post was from 2010, so I was skeptical myself. A bit of searching and I found that there are tons of products based on this tech. Mostly ion water softeners and the like, but maybe that’s a secondary benefit to the pH stability.

Here’s some things I found, haven’t dug deep enough quite yet to see if these will work but it’s a starting place for research.

https://www.walmart.com/ip/Water-Softener-Resin-Media-Replacement-100-Ion-Exchange-High-Quality-Cation-0-25-CuFt/998104541

Looks like 3M even developed a filter around this.

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559

Digging in a bit deeper, it seems the Amberlite CG50 has been replaced. (The article was from 2010 after all.)

I’m not 100% sure which one is the proper replacement, but here’s the table available from Dupont.

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I bet if you can identify the proper replacement you’ll be able to find smaller quantities. They also offer other “branded” IERs. Going to keep reading, this one really has my brain going.

560

My limited understanding is that adding any acid creates the carbolic acid - which is just dissolved C02. That lowers the PH, but then the C02 outgasses from the solution, and the PH goes back up.

But I would expect that to happen pretty fast - a few hours at most. Plus, once the C02 levels equalize with the air in my grow room, the reaction should stop - shouldnt it?

Somehow, circulating/aerating my water, causes an ongoing reaction that never seems to get used up.

561

True for just about anything. Phosphate buffers, potassium, carbonate, citrate, MES, hot coffee, etc. The concentrations before they cause problems is a better question that should be addressed.

Using strong phosphate buffers will throw your nutrient ratios off. Possibly increasing the phosphate, potassium, or sodium to toxic levels.
Carbonate buffers are toxic at relative low concentrations, I think he says 100PPM. One study shows a decline in photosythesis at over 500uM carbonate.
Citrate buffer concentration, I don’t know. I’ve seen papers use it for various research goals as a chelate. Other than that, not clear.
Research studies on MES suggest levels less than ~20 mM show no phytotoxicity.

Keeping in mind, in all cases including resin exchange, you will have to deal with the build-up of toxic levels of minerals over a long period even if the PH seems stable. Also, all of these buffers could potentially sequester certain nutrients.

Which is curious since he didn’t actually include that in his simulation graphs. He did state the citrate concentration referenced to calcium citrate which is one possible complex (potassium, sodium, etc). While, in a different blog post:
https://scienceinhydroponics.com/2009/02/keeping-the-ph-of-your-hydroponic-nutrient-solution-stable.html
where he notes:

As it can be seen, citrate provides very good buffering capacity towards acid pH values while it’s buffering potential towards basic pH values becomes lesser.

I can only conclude that his citrate buffer comments from the first post is based on an exceedingly low concentration to the point of not actually seeing the buffer. We’ve seen a straight citrate buffer (via citric acid) in combination with MC show some buffering improvement at concentrations that are over 5mM. Less than 5mM, no useful improvement on top of the phosphate buffer that is already there. There were no immediately noticeable precipitates at the various concentrations but rather a possible improvement in solubility over a wider range of PH (while ignoring the possibility of long term insoluble precipitates).

Personally, I don’t think I’d consider using a citrate buffer by itself. Although, in combination with other buffers, …

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562

Yeah, thats a good question.

I found this on the DOW site:

AMBERLITE CG50 (type1) is a crosslinked methacrylic type of weakly acidic cation exchange resin powder. The resin has a high concentration of carboxylic groups which serve as the ion exchange site of the resin.

if you Googl;e “crosslinked methacrylic type of weakly acidic cation exchange resin” you come up with some other options.

I found this other resin - Methacrylic Type DIAION™ WK10 Series - that sounds like the same thing - but its available in much larger ‘beads’ that would be much easier to handle.

https://www.diaion.com/en/products/ion_exchange_resins/weakly_acidic_cation/index.html

From that Dow link you posted, I found a few things that may help, but not an exact replacement. Their search function isnt working for me.

The one we want is a WAC = Weak Acid Cation. I ‘thnk’ we need the AMBERLITE™ HPR8300 H version, but Im not at all certain of that. For one thing, that one is Acrylic, and the older version is Meth acrylic.

https://www.dupont.com/content/dam/Dupont2.0/Products/water/literature/177-03612.pdf

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