Mars Hydro 5-Gallon DWC Hydroponic System - Continuous Feed?

[Delps8]

They use the airpump to drive whatever is in the reservoir to kind of spit out across the media. I always thought that a submerged water pump would drive the feed on a schedule.

So with this the system is continuously feeding or circulating through the system.

My plan is to dump/clean/sanitize the reservoirs weekly. Then refill with that weeks target for nutes. I’ve read that some people top with ph’d RO water through the week and others top with nutes. It sounds like there can be a build up of salts with the later.

What I do not want to have to do is meter the water daily and make adjustments, so I am really hoping I can get away with that.

I’m hoping this is the “lazy man’s” set up HAHA

I need a lazy grow after the last 2 that I’ve had haha

I've been using a DWC system since I started growing and, while I understand the enthusiasm, I can't figure out "dump/clean/sanitize…weekly". Unless you've got root rot or some other reason why you've got decaying organic material in the bucket, at best there's no reason to sanitize the bucket and, most likely, you're damaging the bacteria that grow in the res.

If you're doing frequently tissue analysis, you will also be topping off with a solution designed to bring the chemical composition of the nutrient mix with desired range.

If you're not doing tissue analysis, you should top off with plain water. If not, you may run into nutrient imbalances. The reason for this is that there are three distinct categories of rapidity of uptake ini hydro. The chemicals with the fastest uptake are absorbed by the plant within hours. If you're using an EC meter to gauge nutrient strength, you won't know that because those chemicals are not highly conductive. Nonetheless, they're where they should be. - in the plant. If you top off with a nutrient solution with a standard mix, you're adding back the nutrients that have already been taken and the plant will dutifully absorb those. By repeatedly adding nutrient mix, you will, eventually, move levels of the rapidly absorbed nutrients into the toxicity range.

"build up of salts" - the chemicals in nutrients are categorized as "salts". Are you thinking there's a build up? That's not the case. Per above, topping off with water will tend to avoid nutrient issues vs topping off with nutrient mix which will tend to incur nutrient issues.

Another reason to top off with water is that the lowered EC provides something of a mechanism to provide feedback as to when to change the res. If you're using buckets, get the largest buckets you can. The larger the res, the more stable, in terms of pH and EC, your system will be. I use a res that holds 26 gallons and, now that I've learned a few things about reservoir maintenance, it's an absolute joy to work with.

Two paper on reservoir management are attached. In the Bugbee paper, he discusses nutrient uptake in terms of the "mass balance" concept. I found it very helpful, especially in terms of understanding why growers should not use nutes to top off. The second paper, discusses the mechanics of topping off. They're both very helpful.

Another excellent resource is the site scienceinhydroponics.com. The site is run by a PhD. chemist (IIRC) who is the author of HydroBuddy. Take some time to read through the archives. One issue that took a while to sink in for me is that EC is, at best, a marginal proxy for the status of the nutrient solution in your res.

The chart that's floating around here on 420, which I've referred to as "The Wonder Chart" is just plain wrong in some cases. I was thrilled to find something that shed light on the meaning of changes in the reservoir but soon came to learn that it was absolutely incorrect about falling pH being a sign of a problem. My early grow journals document that shit storm that I went through to fix a problem that was a completely expected occurrence in hydro.

The issue? It is completely normal for pH to rise in veg and to fall in flower. Those changes are a result of how plants change their nutrient uptake at different stages of growth.

The underlying concept is that the law of electrical balance requires that the reservoir maintain a state of neutral charge. This simple graphic sheds some light on the details.

I stumbled across a couple of short but helpful videos by Bugbee.

This one is on VPD and how it impacts nutrient uptake.

And this one on how pH impacts nutrient uptake.

 

[Delps8]

Three and a half years into growing with hydro, I finally found a number that I can hang my hat on re. pump size.

I found a paper on my laptop that I wasn't familiar with. It's the "Principles of Nutrient and Water Management for Indoor Agriculture" paper in my posting above, which has among its coauthors both Bugbee and Ferndandez, and Bugbee aerates at the rate of 10% of the volume of the reservoir every minute.

 

[Wastei]

I've been using a DWC system since I started growing and, while I understand the enthusiasm, I can't figure out "dump/clean/sanitize…weekly". Unless you've got root rot or some other reason why you've got decaying organic material in the bucket, at best there's no reason to sanitize the bucket and, most likely, you're damaging the bacteria that grow in the res.

It's important to state that a wide range of bacteria cultures are not desirable in water cultures since they often do more negatives than benefits competing for survival and leaving a window for bad ones to flourish. If OP choose to go the bacteria route I believe it's important to state its function in hydro?

The only bacteria culture you should add in hydro is "bacillus amyloliquefaciens", what you commercially find in Hydroguard or a better product is SouthernAG Garden Friendly Fungicide, the difference is the concentration. SouthernAG being 98% pure compared to Hydroguard 0.038%.

Their purpose of adding either bacteria culture or oxidizers is to clean the root stomata from biofilm preventing direct and optimal uptake of ions in the nutrient solution. You don't want bacteria to be the transporter of nutrients, they've already readily available. They should only work at outcompeting bad bacteria cultures.

Hope that helps OP out.


Cheers!

 

[Delps8]

It's important to state that a wide range of bacteria cultures are not desirable in water cultures since they often do more negatives than benefits competing for survival and leaving a window for bad ones to flourish. If OP choose to go the bacteria route I believe it's important to state its function in hydro?

The only bacteria culture you should add in hydro is "bacillus amyloliquefaciens", what you commercially find in Hydroguard or a better product is SouthernAG Garden Friendly Fungicide, the difference is the concentration. SouthernAG being 98% pure compared to Hydroguard 0.038%.

Their purpose of adding either bacteria culture or oxidizers is to clean the root stomata from biofilm preventing direct and optimal uptake of ions in the nutrient solution. You don't want bacteria to be the transporter of nutrients, they've already readily available. They should only work at outcompeting bad bacteria cultures.

Hope that helps OP out.


Cheers!

I've only ever used Hydroguard. I'll take a look at SouthernAG Garden Friendly Fungicide since I need a new bottle for my upcoming grow.

[clicks over to Amazon]

That'll do it. Thanks for the heads up.

 

[Ke0ncp]

Nice find. I have a bluelab Guardian monitor that does the same for only five times the price. For seventy bucks you could put one in each bucket. Buy some calibration fluid (4.0 pH and 7.0 pH). I calibrate mine once a month.

My thoughts exactly!@

If you're not doing tissue analysis, you should top off with plain water. If not, you may run into nutrient imbalances. The reason for this is that there are three distinct categories of rapidity of uptake ini hydro. The chemicals with the fastest uptake are absorbed by the plant within hours. If you're using an EC meter to gauge nutrient strength, you won't know that because those chemicals are not highly conductive. Nonetheless, they're where they should be. - in the plant. If you top off with a nutrient solution with a standard mix, you're adding back the nutrients that have already been taken and the plant will dutifully absorb those. By repeatedly adding nutrient mix, you will, eventually, move levels of the rapidly absorbed nutrients into the toxicity range.

Good to know and thanks for posting the data. I will have to dive into this tonight!

"build up of salts" - the chemicals in nutrients are categorized as "salts". Are you thinking there's a build up? That's not the case. Per above, topping off with water will tend to avoid nutrient issues vs topping off with nutrient mix which will tend to incur nutrient issues.

Understood and I think that is what I was leaning towards. Obviously there comes a point in which you need to top back off with nutes. But it is not like my current grow with a SIP and ProMix which equals feed at every watering.

This will be a fun ride that's for sure. And I am most certainly bound to fuck it all up mid grow and then recover, at least if I want to keep my fuck it up streak going!!

 

[Delps8]

My thoughts exactly!@

Good to know and thanks for posting the data. I will have to dive into this tonight!

Understood and I think that is what I was leaning towards. Obviously there comes a point in which you need to top back off with nutes. But it is not like my current grow with a SIP and ProMix which equals feed at every watering.

IIRC, the CannaStats paper talks about replacing the res after you've added back the equivalent amount in RO. Another approach is to replace after a 50% drop in EC. Either of those will work but consider that CannaStats metric is that you should have three gallons of res for each square foot grow space.

[opens document]

CannaStats:

"At a reservoir size of 3 gallons/sq ft...." - OK got that one right

I did a swing and miss with the 50%:
"Reservoir life ends with a TDS of approximately 75% that of the starting TDS (depending on source water)
- minus 25% TDS tends to coincide with the point at which buffering power is about to be lost and pH begins to become unstable""

I've allowed EC to drop to 50%± because that's where pH has started to get squirrely so 25% might be a better metric.

This will be a fun ride that's for sure. And I am most certainly bound to fuck it all up mid grow and then recover, at least if I want to keep my fuck it up streak going!!

LOL - I understand that completely.

I poisoned my last grow. Yup, Mr. F'ing Checklist here started adding H2O2 to the water in the humidifier after getting tired of having to clean it every few days/week. Normally, my plants get pretty hefty but that wasn't the case for that grow. It took a while before I noticed that the foliage that was closest to the humidifier looked…stunted.

It was "Oh, f'ck me!" when I figured out what I had done. I call it my Klaus von Bulow grow.

 

[Ke0ncp]

I've allowed EC to drop to 50%± because that's where pH has started to get squirrely so 25% might be a better metric

So at -25% of starting PPM you top back up with nutes and water until that point? Or let me reword that. Anything +25% below target PPM gets topped with water. Once I hit 25% or more off of target it’s time to top with nutes? Or am I not reading that correctly?

I am using a nute calculator, I think you referenced it here or somewhere else but I’ve not used it before to “top up PPM”, and only to determine the amount of nutes and additions to hit my target %. Are you using it for that or another tool / equation?

And as far as f’ing things up , well that’s my specialty! I am really a pro at it!!

 

[Delps8]

So at -25% of starting PPM you top back up with nutes and water until that point? Or let me reword that. Anything +25% below target PPM gets topped with water. Once I hit 25% or more off of target it’s time to top with nutes? Or am I not reading that correctly?

Top up as much as you wish with plain water, RO or tap. As you do so, the EC of the nutrient solution will drop. Once EC has fallen to 75% of the original EC, that's a good, general indicator that the nutrient solution should be replaced.

E.g. -start at EC 1.0, add water daily for X days and EC drops gradually. Once it hits EC 0.8 or so, do a fresh res.

CannaStats says that a 25% drop is about the time where pH starts to wander so do a fresh resh.

Another guideline that's discussed is to swap the res when you've added back a volume equal to the volume of the res.

There are no hard and fast rules because there are too many variables but those are two pretty good ways to know when to do a new res.

Check out scienceinhydroponics.com on this, as well. Lots of interesting reading there. Some of it is too deep in the weeds for me but, overall, it's a good resource.

I am using a nute calculator, I think you referenced it here or somewhere else but I’ve not used it before to “top up PPM”, and only to determine the amount of nutes and additions to hit my target %. Are you using it for that or another tool / equation?

No, I do not add nutrients; I add only RO. The Bugbee paper explains why adding in nutrients can cause nutrient issues.

The assumption is that nutrients are all removed at the same or at a similar rate. That is not correct.

I think it's N, P, and K that are gone in a matter of a day or so. But they're only gone from the res and they're in the plant where they need to be. That's the concept of "mass balance" - it's either in the bucket or in the plant.

If N, P, and K (check the Bugbee paper to see which ones are taken up the fastest - I've highlighted that section ) are taken up very quickly and you come along and add more nutrient solution, the plant has to take up those chemicals because they're taken up along with water that's needed for transpiration.

That's why it's good to understand and monitor VPD because the vapor pressure deficit between the water-filled leaves and the outside air has to be equalized and the plants do that via transpiration. Physical processes are all about seeking stasis so highs move to lows; air, water, temperatures, all are changes seeking equilibrium.

Plants have to release water to equalize the difference in the vapor pressure and when they do, the have to take in water. If you keep dumping in more chemicals, those chemicals have to be taken up by the plant and that will, eventually, result in nutrient levels moving from the sufficiency range into the toxicity range.

Of course, that may happen or it may not. If you swap the res frequently enough, the worst that will happen is that you're shoveling chemicals into your plants but not so much that you're damaging them. "In the small", for the home grower, it's not that big an issue. OTOH, when you've got a lot of plants, it drives up cost and takes more time. My approach, in general, is to try to do things well, even "in the small", because if I know how to do it well, why not do it well.

I do a new res three or four times over the course of a 110 day grow (Yeh, plants take forever and I've settled on the idea that's because they're floating around in 26 gallons of nutes.) That's really nice to have to do only a few res swaps. Also, pH is really stable. That's a moot point now that I use a doser but before I put that into service, the only time pH would change dramatically was in the first 10 days of flower. (We don't talk about the shit show that a "bloom booster" caused!) Other than that, all of the factors of doing the little things have helped add up to a lot of my grows being "Maytag repairman" level of excitement (you're in your 40's so ask your dad about "Maytag repairman" )

And as far as f’ing things up , well that’s my specialty! I am really a pro at it!!

 

[Sativa1970]

In my experience one out of a hundred plants has had root rot issues. I have never used any rot prevention products other than maybe12oz of peroxide over the last decade.. That one plant was due to the res hitting mid 90sF and my air pump stopped at the same time. Dropped the temp, plugged in a new pump, added a shot of peroxide to quick boost O2 and she continued to harvest every time. O2 kills bacteria and warm water holds less O2. Keep the res clean, cool well oxygenated, dark, and nothing can not grow to be an issue.

If EC drops you are under feeding top up with a stronger nutrient water mix.
If EC rises you are over feeding top up with PH water check EC again.
If your EC stays stable but PH rises or drops you have off balance NPK or intruder. Change res.
When water drops, EC and PH are unchanged you found the plants magic EC number.

 

[Ke0ncp]

If EC drops you are under feeding top up with a stronger nutrient water mix.
If EC rises you are over feeding top up with PH water check EC again.
If your EC stays stable but PH rises or drops you have off balance NPK or intruder. Change res.
When water drops, EC and PH are unchanged you found the plants magic EC number.

Makes sense to me! And easy enough to do as well

 

[Sativa1970]

The PH is going to naturally drift around .3 up and down after setting to 5.8. Below 5 or over 7 with good EC is when res change is considered. Try to take your readings at the same time of day.

 

[Ke0ncp]

So doing some more research, would this actually be considered RDWC or no because it doesn’t have a separate reservoir?

 

[Zeefarmer]

OK So I have decided to jump into DWC for my next grow and have this coming from @Mars Hydro. From what I can gather it looks to be a continuous feed system? Am i reading this correctly?

My plants are using 4 gallons of water or MORE per day.
5 gallon bucket IMO is not big enough for the reservoir size .

 

[Delps8]

So doing some more research, would this actually be considered RDWC or no because it doesn’t have a separate reservoir?

In common parlance, it's RDWC is there's an external res but, when you get into the research world, it's not. And that's something to keep in mind when reading the paper by Bugbee and others.

Look up "Nutrient Film Technique" as an example of RDWC in the agricultural world. This is one example of true RDWC.

The key point for "RDWC" is that the roots aren't in a large vessel in a with a largely static amount of nutrient solution water that has solution flowing in and out of the vessel. Instead, the nutrient solution flows through a shallow chamber underneath the plant and the roots are immersed in a small amount of nutrients.

The difference is important because in true RDWC, evaporation of the nutrient solution is a significant issue whereas in cannabis RDWC, evaporation is measurable but insignificant.

My setup is DWC but not RDWC. Systems from PA Hydro and Current Culture, to name just two, that have an external res are considered RDWC in the cannabis world but to an ag person, since the roots are always immersed in a large volume of water, it's DWC.

 

[Delps8]

It's important to state that a wide range of bacteria cultures are not desirable in water cultures since they often do more negatives than benefits competing for survival and leaving a window for bad ones to flourish. If OP choose to go the bacteria route I believe it's important to state its function in hydro?

The only bacteria culture you should add in hydro is "bacillus amyloliquefaciens", what you commercially find in Hydroguard or a better product is SouthernAG Garden Friendly Fungicide, the difference is the concentration. SouthernAG being 98% pure compared to Hydroguard 0.038%.

Their purpose of adding either bacteria culture or oxidizers is to clean the root stomata from biofilm preventing direct and optimal uptake of ions in the nutrient solution. You don't want bacteria to be the transporter of nutrients, they've already readily available. They should only work at outcompeting bad bacteria cultures.

Hope that helps OP out.


Cheers!

My bottle of GFC arrived but no instructions for use in hydro. I called their North Carolina office and that was a dead end. :-(

What's the recommended dosage?

 

[Wastei]

In common parlance, it's RDWC is there's an external res but, when you get into the research world, it's not. And that's something to keep in mind when reading the paper by Bugbee and others.

Look up "Nutrient Film Technique" as an example of RDWC in the agricultural world. This is one example of true RDWC.

The key point for "RDWC" is that the roots aren't in a large vessel in a with a largely static amount of nutrient solution water that has solution flowing in and out of the vessel. Instead, the nutrient solution flows through a shallow chamber underneath the plant and the roots are immersed in a small amount of nutrients.

The difference is important because in true RDWC, evaporation of the nutrient solution is a significant issue whereas in cannabis RDWC, evaporation is measurable but insignificant.

My setup is DWC but not RDWC. Systems from PA Hydro and Current Culture, to name just two, that have an external res are considered RDWC in the cannabis world but to an ag person, since the roots are always immersed in a large volume of water, it's DWC.

It sounds like you're confusing RDWC with NFT? Nutrient Film Technique? A RDWC system might be completely without a traditional control reservoir depending on design choice? I'm afraid you mix a lot of terminology when you write your comments?

The simplest RDWC system you could possibly make is having two big containers connected together to get equal and even water levels and then having a recirculating pump move water from one container to the other. That's recirculating but not in the traditional under current systems sense with a control reservoir and the end of the rows.

NFT(Nutrient film technique) has very little to do with RDWC(Recirculating deep water culture). I'm afraid your comment is more confusing than helping for OP? The terminologies are not interchangeable.

What is "Cannabis RDWC"? I'm confused... I argue the key point for RDWC is that the system is recirculating in a deep water culture system? Vessel or container sizes has very little to do with the type of system you're trying to explain even though a bigger system with larger volume is more stable in terms of keeping temps down and EC and pH in range.

Cheers!

 

[Wastei]

My bottle of GFC arrived but no instructions for use in hydro. I called their North Carolina office and that was a dead end. :-(

What's the recommended dosage?

I would mix ~1.5ml GFF(98%) to 1 gallon water to make Hydroguard (0.038%) and then follow their recommendations 2 ml per gallon. It's pretty neat since they contain the same bacteria strain. If stored properly it will last you years instead of grows.

Bacillus amyloliquefaciens seem to be very hardy and stable and I even bought it in granular form during my visits in Asia.

They say less is more when it comes to bacillus amyloliquefaciens in DWC. People have gone through different scenarios on other forums and some struggled in DWC at higher concentrations.

People use higher concentrations growing DTW in regular containers ie peat, coco coir. People use ~0.5ml GFF per gallon of water . I do not use this myself since I'm not able to source it but a good friend of mine use it in higher 70's in his reservoir without any problems but he also grows in DTW coir.

The Dilution calculator in my signature comes very handy when you need to calculate and mix different stock solutions and their concentrations.

Cheers!

 

[Delps8]

I would mix ~1.5ml GFF(98%) to 1 gallon water to make Hydroguard (0.038%) and then follow their recommendations 2 ml per gallon. It's pretty neat since they contain the same bacteria strain. If stored properly it will last you years instead of grows.

Bacillus amyloliquefaciens seem to be very hardy and stable and I even bought it in granular form during my visits in Asia.

They say less is more when it comes to bacillus amyloliquefaciens in DWC. People have gone through different scenarios on other forums and some struggled in DWC at higher concentrations.

People use higher concentrations growing DTW in regular containers ie peat, coco coir. People use ~0.5ml GFF per gallon of water . I do not use this myself since I'm not able to source it but a good friend of mine use it in higher 70's in his reservoir without any problems but he also grows in DTW coir.

The Dilution calculator in my signature comes very handy when you need to calculate and mix different stock solutions and their concentrations.

Cheers!

Many thanks for the info.

I'll check out the calculators - never now when they'll coming handy.

"If stored properly it will last you years instead of grows." - I ditched my bottle of Hydroguard because it was 18 months old. Better safe than sorry.

Garage temps range from 70 to high 80's so keep the bottle in the house (68-82)?

 

[Delps8]

It sounds like you're confusing RDWC with NFT? Nutrient Film Technique? A RDWC system might be completely without a traditional control reservoir depending on design choice? I'm afraid you mix a lot of terminology when you write your comments?

The simplest RDWC system you could possibly make is having two big containers connected together to get equal and even water levels and then having a recirculating pump move water from one container to the other. That's recirculating but not in the traditional under current systems sense with a control reservoir and the end of the rows.

NFT(Nutrient film technique) has very little to do with RDWC(Recirculating deep water culture). I'm afraid your comment is more confusing than helping for OP? The terminologies are not interchangeable.

What is "Cannabis RDWC"? I'm confused... I argue the key point for RDWC is that the system is recirculating in a deep water culture system? Vessel or container sizes has very little to do with the type of system you're trying to explain even though a bigger system with larger volume is more stable in terms of keeping temps down and EC and pH in range.

Cheers!

Sorry that you're confused.

What I've seen is a two different types of RDWC - in the cannabis world, RDWC is used to describe a DWC system with an external reservoir. Current Culture and PA Hdyro sell those sorts of systems. But those are closed systems.

In the ag world, the recirculating aspect involves flowing water over the substrate and I linked to one such type system. Those systems don't have the "one plant in a big bucket + a res" design that's sold as RDWC in the cannabis world.

If you have a different opinion//can shed some light on it, please do.

 

[Ke0ncp]

So still wondering, and I probably missed it, does this system I have classify as a rwdc since it is in fact recirculating, even though it doesn’t have an external reservoir?