Res/Nutes Change Frequency

My English sucks, so does my Chemistry

I meant more something that you can compare CO to CO2. The first one is very poisonous.
I thought perhaps something could also happen to an element in the nutes.
But again: I have no clue at all.

Keesje said:

My English sucks, so does my Chemistry

I meant more something that you can compare CO to CO2. The first one is very poisonous.
I thought perhaps something could also happen to an element in the nutes.
But again: I have no clue at all.

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I hear what you’re saying I think. Basically you are wondering if new compounds can form. I imagine that yes, over time the mixture of various compounds that are in the reservoir will breakdown to some extent and may even form new/other compounds eventually. For example, I imagine that the carbonate system comes into play where pH could change over time as carbonate, bicarbonate, free hydrogen and hydroxide ions all interact and change relative to one another. This is common in wastewater treatment and hydrogeological

Essentially, our reservoirs act like little organic chemistry experiments which will affect pH, and potentially nutrient availability.

I’m hardly an expert on this and haven’t looked at this kind of stuff in years. I’m ten years outta college but did organic chemistry and engineering - I imagine that all sorts of things take place in a reservoir over time.

Good luck!

DarthVaper84 said:

I hear what you’re saying I think. Basically you are wondering if new compounds can form. I imagine that yes, over time the mixture of various compounds that are in the reservoir will breakdown to some extent and may even form new/other compounds eventually. For example, I imagine that the carbonate system comes into play where pH could change over time as carbonate, bicarbonate, free hydrogen and hydroxide ions all interact and change relative to one another. This is common in wastewater treatment and hydrogeological

Essentially, our reservoirs act like little organic chemistry experiments which will affect pH, and potentially nutrient availability.

I’m hardly an expert on this and haven’t looked at this kind of stuff in years. I’m ten years outta college but did organic chemistry and engineering - I imagine that all sorts of things take place in a reservoir over time.

Good luck!

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This is what Dr. Daniel Fernandez said about the subject:
Add in-line UV filters and carbon filters. It is fundamental to ensure no microorganisms contaminate your nutrient solution. For this reason, online UV-filters are necessary to keep the nutrient solution as sterile as possible. Carbon filters are also very useful as they remove plant exudates that can contaminate the solution and cause problems within the crop itself. Many of these exudates are food for microorganisms, others are plant hormones that might cause unwanted responses in the plants. However both carbon filtration and UV filters can cause some issues – such as the destruction and adsorption of heavy metal chelates – so it is important to use chelates that are more resistant to UV and have less affinity for carbon filters to alleviate these problems.

Keesje said:

This is what Dr. Daniel Fernandez said about the subject:
Add in-line UV filters and carbon filters. It is fundamental to ensure no microorganisms contaminate your nutrient solution. For this reason, online UV-filters are necessary to keep the nutrient solution as sterile as possible. Carbon filters are also very useful as they remove plant exudates that can contaminate the solution and cause problems within the crop itself. Many of these exudates are food for microorganisms, others are plant hormones that might cause unwanted responses in the plants. However both carbon filtration and UV filters can cause some issues – such as the destruction and adsorption of heavy metal chelates – so it is important to use chelates that are more resistant to UV and have less affinity for carbon filters to alleviate these problems.

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The following excerpt is from Maximum Yield so not always the best source but this info seems to have some traction:

In the early days of hydroponics there was concern that the organic matter, dead root cells and compounds released by roots would accumulate in the limited root zone and nutrient solution to the point where it promoted disease and retarded growth.

It was quickly proven that this isn’t the case, and we have come to understand in more detail how the dynamics of a restricted root zone works. Methods designed to disinfect and remove organic compounds or frequent nutrient solution changes were sometimes used to control the buildup of these exudates, but studies have shown this is not necessarily beneficial.

When microbial populations are permitted to develop in healthy hydroponic systems, they break down and metabolize carbon compounds in the root zone or nutrient solution, so this sort of buildup doesn’t occur when all is working well.

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I did flood and drain for a long time, in multiple houses at once, and had great results from running my reservoir for the whole flowering cycle without dumping. So IME it's ok so long as you have things dialed in and the plants are healthy.

Renfro said:

I did flood and drain for a long time, in multiple houses at once, and had great results from running my reservoir for the whole flowering cycle without dumping. So IME it's ok so long as you have things dialed in and the plants are healthy.

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Perhaps you also have the answer to this then:
Dr. Daniel states this: In a normal recirculating setup the EC of the solution in the main tank will tend to increase with every irrigation while the total volume of the solution will decrease. This happens because healthy plants always absorb more water than nutrients, which means any measure that’s proportional to concentration – such as the EC – will tend to increase as the amount of water goes down.
So when water level drops, and EC rises > healthy plants, according to Dr. Daniel

But there is also this well known diagram where it is stated that if water drops and EC rises, you have to lower your EC.
And it is also says in this diagaram that when water level is falling and EC stays the same, you have ideal conditions.



Who is right?
Dr. Daniel or the diagram?

Keesje said:

Who is right?
Dr. Daniel or the diagram?

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Your plants are right lol. If they are healthy and happy I don't think it matters if the EC stays the same or drops a little.

FWIW, In my flood and drain, the water drops and the EC remains pretty much the same but when I top off the water level the PPM needs a little boost.

Renfro said:

FWIW, In my flood and drain, the water drops and the EC remains pretty much the same but when I top off the water level the PPM needs a little boost.

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Why is that?
Because you want your EC to slowly increase during your bloom?

Keesje said:

Why is that?
Because you want your EC to slowly increase during your bloom?

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Renfro will answer this better, but I believe the water level dropping with static EC just means the nutrient uptake is relatively low compared to the total volume of concentrated nutrient water.

I imagine Renfro runs a pretty big reservoir and although water level drops (plant uptake and perhaps other minor evaporative losses), the plants just don’t take up that much nutrients.

And of course, when topping off the water to the standard level with presumably 0 ppm water, the EC then needs to be increased due to the dilution of adding RO water.

You may have already inferred all this so my apologies if I seem patronizing!

Keesje said:

Why is that?
Because you want your EC to slowly increase during your bloom?

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It tops off daily by float on a timer and I maintain PPM with add backs (usually bloom add backs).

Renfro said:

It tops off daily by float on a timer and I maintain PPM with add backs (usually bloom add backs).

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Ah, I think I misunderstood your earlier reply.

Keesje said:

Ah, I think I misunderstood your earlier reply.

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All good. I was a little confused lol.

Renfro said:

All good. I was a little confused lol.

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I sometimes miss things because English is not my first language.

Keesje said:

I sometimes miss things because English is not my first language.

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I can totally understand that, my excuse is just being high lol.

I've only grown in R/DWC. I used to change my res weekly, new water, new nutes. This was necessary as I was doing all kinds of weird shit to the feed ratios when I was learning. After a few grows under your belt you'll learn what the plants want. These days I don't change my res but I still need to top up fresh solution. Once you hit that sweet spot you can get very close to giving the plants exactly what they need. The best I've done so far is a 20/10 ppm drop over the course of a week from 800ppm/400ppm to 780/390. During the entire grow I haven't gone above or below 50ppm difference from my base solution. So far I'm at the end of week two flower and they were vegging for four weeks. The total volume of solution is 320 gallons. That may make things more stable I dunno but my ppm has been consistent the whole time. The only thing I add when the ppm starts dropping is cal/mag but the NPK + essentials have mostly stayed the same.

petedavid said:

Hi guys,

I run a flood and drain systems, with 100gal res's that I change every 2 weeks. Recently, in a veg tent, I have seen slow/miscolored growth towards the end of a 2 week cycle (with E.C and PH are fine). I feel like I need to drop the res change frequency to every 10 days and see if this phenonemon shows again, however, I don't want the extra work of more res changes.

How often do you guys change your nutrients? Should I investigate changing every 10 days, or even less?

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I am running an ebb and flow 3 feed a day cycle. I simply keep a spare reservoir of nutrients premixed. I will top off the other reservoirs with it until it is empty. Then it is easy to remix another full concentration batch in the spare res. I continue to top up reservoirs until they are 20 days old, then I dump, clean, and start over. I use simple paper labels on the lids to note each reservoirs last fresh refill. I also keep my reservoirs spaced out one day from one another to avoid that very long day off redoing all reservoirs at once.