When To Change Dwc Reservoir?

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OldManRiver

OldManRiver

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I've got a ten gal DWC system. The plants are almost a month old, growing rapidly. On my last reservoir change, initial ppm was about 980, ppm a week later is 880. Water has a ppm of about 210. I have changed the nutes once since starting, about a week ago. I am running about 80% strength of the manufacturer's recommended maximum veg dose; any stronger and the chem dawg starts throwing some brown tips.

When do y'all change the reservoir? How often, or at some level of ppm decline?

If it matters, I'm running General Hydroponics trio. Been keeping the ph between 5.5 and 5.8.

Pic from two days ago, they are two inches taller today, before tucking into the screen. The plants are growing very rapidly and well.
 
Indoor9 4
J

johnny prince

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is that ppm on a .5 or .7 scale . When I ran this type of system I had mine usually about 400 ppm at .5 scale . The tap water was 107 ppm. I would top off every few days and a full reservoir change every 2 weeks. I used hydro guard as well.
 
fatawa

fatawa

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How often, or at some level of ppm decline?
already said but once a wk n they stay happier easier.no more than once every 2wks(imo)..u will c best growth rates doing it wkly.as for ppm check it ea day for 3-4days,if there drinking more then 50ppm a day then u can up the overall value slowly.dialed n wud b tech no drop n ppm over the 3-4days.but i like to c a 10-20ppm drop a day,just so u kno there drinking nutes.but if u get to point where ppm raises over them few days yur too high
 
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Shawnery

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So I'm a newbie so don't listen to a freaking thing I say but I just feel like it's necessary to share this. I understand that it's best to change your Reservoir every week 2 weeks at the most but what if you don't have to.

I've traversed a number of marijuana growing sites and through my journey I found many outliers who don't change their water at all. I followed one person's thread and they went from their first grow changing out the water every week. Then in their second grow they cleaned out their water once a month. Then on his third grow he decided not to change out his water at all.

Through all three separate grows there was no discernible difference between yield or quality. I understand the argument to why you need to change out your water but this antidotal evidence puts that strongly into question. Has anybody here actually gone the entire grow without changing out their water and can point to some disasterous experience they had through the process or is this just information that has been handed down from grower to grower without ever questioning it?
 
King Julien

King Julien

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Twice for the whole grow.if your shit is right you won't need to

It is true, but it does take some finesse in the whole "dialing in" department.

I've gone 2+ months in veg with no problem and only PH'd once a week. I've also only changed water twice in a 9 week flowering. Once after 4 and a half or 5 weeks and once for a flush at the end.

Usually though I only change every 2 weeks unless they are REALLY drinking up a ton of water fast. If I just keep having to add nutrient solution over and over and over days in a row I switch out more often. They don't drink I do the same thing with a bit weaker nutes if I think they look like they want it. But I also don't really check ppms or PH so it's my way of being extra lazy.

Use RO water, dial in your nutes, watch your PH, and you can never change your nutes and get a harvest. It won't be as good as if you change it once for transition or once more for flushing but you can do it and pull weight. I've seen it done on the interwebs elsewhere as well.
 
fatawa

fatawa

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Just my opinion but the whole purpose of dro is being surgically clean..you get that clean dro taste from rezi changes.y let it sit n same water diluted down multiple times..basicaly same concept of dirt then n my eyes.just my opinion
 
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heisen

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Do your plants drink?I'm in a 17 gallon system and mine drink 10 to 12 gallons a week so no it's not the same diluted water
 
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Shawnery

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Just my opinion but the whole purpose of dro is being surgically clean..you get that clean dro taste from rezi changes.y let it sit n same water diluted down multiple times..basicaly same concept of dirt then n my eyes.just my opinion

I understand this concern but I have personally read a number of threads that have stated this does not happen. Of course if you have other issues you can have problems but not from solution changes or lack of. I'm talking about people who have done it a multiple of ways and found not changing at all had no effect. Of course you still need to run plain water at the end to washout the nutes fron your plants but why would you have to wash them out multiple times?
 
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heisen

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I understand this concern but I have personally read a number of threads that have stated this does not happen. Of course if you have other issues you can have problems but not from solution changes or lack of. I'm talking about people who have done it a multiple of ways and found not changing at all had no effect. Of course you still need to run plain water at the end to washout the nutes fron your plants but why would you have to wash them out multiple times?
The plants drink most of the water.being chilled the older water actally stabilizes the ph so far less ph swings.if I was not on a chiller I would probably change every week
 
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Shawnery

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As long as your temps stay around 68 or so you should be fine? If you run a chiller or not?
 
King Julien

King Julien

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The plants drink most of the water.being chilled the older water actally stabilizes the ph so far less ph swings.if I was not on a chiller I would probably change every week

I don't use a chiller but I also use calcium hypochlorite to keep things sterile. I own a couple chillers actually. A half and a quarter horse. I just never got around to building the RDWC for it so the one I got for it, the smaller one, is just sitting there.

One day I'll likely go RDWC and use a chiller but only for more DO and at that point why not? For now though I'm managing. I just keep my temps down and keep it sterile and things seem to get along alright.

My water temps generally stay a few degrees below the temp of the bottom of the tent. I keep a couple thermometers with long probes on them and dual readouts so I can monitor ceiling, canopy, and floor temps. They also have memory so I know the highest and lowest they've gotten since I last checked on them.

My floor temp is 74-75 with lights on so my water temp says around 71-72. Not far off but I know for a fact without the calcium hypochlorite it would be a rotting nightmare. I know for a fact because it's what happens if I go more than a week or so without using it.
 
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Shawnery

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I add h202 to mine weekly clean out mine during the grow and it always helps with any build up and a temporary spurt of growth.
 
Growing King

Growing King

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When you leave the water unchanged, every time you feed you're adding more NPK to your res, if your plant uses all of the N and P but left some K then next time you feed there will be an excess of K. If you let these imbalances continue then things can go downhill fairly quickly.
 
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Shawnery

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People continue to say this but if you do some research you will see it doesn't happen. You're more likely to have an issue due to ph level in terms of nutrient uptake. I've read many hydroponic sites about this subject and there are many who agree obsesive changeouts are a waste of money. In fact there are s9me who belief changeouts are an opening for negative episodes.

Everyone can do and believe what they want but it's hard to argue with real world evidence. The only reason not to believe the evidence is if you believe people are purposely offering untruthful experiences and for what reason.
 
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heisen

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When you leave the water unchanged, every time you feed you're adding more NPK to your res, if your plant uses all of the N and P but left some K then next time you feed there will be an excess of K. If you let these imbalances continue then things can go downhill fairly quickly.
plants don't choose what they eat at the roots lol.thats like saying there like a kid in front of a plate of food.what your saying is simply false.if plants got to choose what we gave them than we would never burn plants.they take in everything that's available.this is why we increase p and k during flower and decrease N so that it is less available.
Nutrient change outs in recirculating DWC is NOT necessary if everything is in check.Plants take in alot of water that are healthy and receiving the proper amounts of light.This water contains the solution and goes into the plant growth.Plant growth does not come from thin air.It comes from the water and the nutrients in the bottles.A well tuned DWC can go an entire grow without a changeout.I change mine twice during the entire grow and have never had issues with anything.As a matter of fact i think you do more harm than good shocking the plants with change outs every 2 weeks.My plants get balanced and stay that way.
I have these plants going now and have changed there nutes once so far and that was when i transitioned from 1 to 2 ratios.they are in a 14 gallon system and drinking 2 gallons a day.so in 14 days they will have drank 28 gallons of nutrient solution.That is twice the amount of the system they are inMe changing out the solution would be defeating the purpose.It would be throwing away money for nothing when the plants are drinking twice the amount of the total volume available in 2 weeks.Once i stopped shocking my plants with change outs are started getting healthier looking plants.But it also requires a fine tuning which i explained my technique in perfecting scotts OG in my sig
3 weeks into flower and 1 changeout since i put them in buckets
20171010 001627


Never changed these out once

20170403 222736


Or these

20170807 231436


20170810 191948



These i never changed at all once.They were autos.

20170709 013624
 
Growing King

Growing King

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plants don't choose what they eat at the roots lol.thats like saying there like a kid in front of a plate of food.what your saying is simply false.if plants got to choose what we gave them than we would never burn plants.they take in everything that's available.this is why we increase p and k during flower and decrease N so that it is less available.
Nutrient change outs in recirculating DWC is NOT necessary if everything is in check.Plants take in alot of water that are healthy and receiving the proper amounts of light.This water contains the solution and goes into the plant growth.Plant growth does not come from thin air.It comes from the water and the nutrients in the bottles.A well tuned DWC can go an entire grow without a changeout.I change mine twice during the entire grow and have never had issues with anything.As a matter of fact i think you do more harm than good shocking the plants with change outs every 2 weeks.My plants get balanced and stay that way.
I have these plants going now and have changed there nutes once so far and that was when i transitioned from 1 to 2 ratios.they are in a 14 gallon system and drinking 2 gallons a day.so in 14 days they will have drank 28 gallons of nutrient solution.That is twice the amount of the system they are inMe changing out the solution would be defeating the purpose.It would be throwing away money for nothing when the plants are drinking twice the amount of the total volume available in 2 weeks.Once i stopped shocking my plants with change outs are started getting healthier looking plants.But it also requires a fine tuning which i explained my technique in perfecting scotts OG in my sig

Hi there all undercover PhD Agronomists,

I'll rephrase what I meant by "nutrients going out of whack if you don't change your res" to be more technical for all that want to get more in-depth info and didn't like my PG-13 version.

Plants indeed do not eat what they want to eat, the plasmodesmata works a little more complicated than that. Nutrient absorption in plants works via osmosis, polarity, and ion exchanges. And they do, mostly eat, what we give them. BUT NOT NECESSARILY in the ratio that we give it to them. For example, if somehow you had a nutrient solution that had 10-10-20 NPK, plus 5 Ca, 5 Mg, and 5 S, and 1% Fe (JUST AN EXAMPLE MIX). It doesn't necessarily mean that your plant will be absorbing everything exactly how you are giving it to them and in that ratio, Why? because ions do not freely exist in the world, elements exist only as molecules to find equilibrium. Some molecules are easier broken by plants than others are. For example, the plant will more easily consume Nitrogen if the raw ingredient was Calcium Nitrate than if the raw ingredient was Urea. It takes longer for the plant to turn urea into absorbable nitrogen than it does when it is already in a nitrate form.

Also, every strand has a slightly different metabolism and nutrient companies make GENERALIZED formulas with different chelator molecules like EDTA and DTPA, fulvics and a variety of plant extracts such as yucca that further aide in faster absorption of SOME elements like iron, magnesium, calcium, and phosphorous; but not others like nitrogen and potassium.

So, when I gave you all the PG version I was wrong to do that and I should have written this long ass essay about it. But when you say that ALL PLANTS eat/consume equal amounts of the ingredients found inside of the bottles just because you are feeding it to them - you are even wronger. They indeed don't chose, WE DO IT for them by feeding them the nutrients; and in turn, the nutrients themselves send the entire solution out of whack after about two weeks. The plants by far will also consume way more water than they do the nutrients dissolved in it, this means that the concentration of solute to the solvent will increase (the TDS will increase), making the solute go further off track; Calcium will bind to sulfur making Calcium Sulfate, Iron will attract to Sulfur making Iron (III) Sulfate, and the Carbon from most of the plant extracts that are sure to be found in all of these nutrients will make Calcium Carbonate and Magnesium Carbonate - all of which are either insoluble or very difficult for plants to breakdown and consume.

SOLUTION: Change the res every 2 weeks for optimal nutrient delivery and add pH'ed water frequently to your res to avoid these molecules from binding; unless you are an undercover PhD Agronomist like heisenbubble.
 
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