Water Level Recommendations for Kratky and DWC

[ERR0R1755]

The water level drops down as the plant drinks the nutrient solution - you start with the water level touching the net pots / growing medium, and once the plant starts growing roots, you keep the water level down a bit so that it doesn't grow algae on top, and so that the plants don't drown.

[ERR0R1755]

Feb 10, 2022 3:25:34 GMT -5 maskedsonnet said:

Those are super helpful!! I’m still very much a n00b when it comes to Kratky and was actually wondering how far I should bring up the water when it got to be that time!! Do you have any hints on nutrients? I’ve started wondering a bit how often I should be replenishing them, but haven’t really found a solid answer yet. Should I be feeding every two weeks like with AG since I’m keeping it to small doses instead of adding everything the plant would need at the very start? I didn’t think the “add it all upfront” method would work well with these experiments, and everything I’ve found on Google so far has just been “add it all from the start” with no experimentation with longer-term projects in small containers like what I’m trying to do here. It’s all been huge containers that wouldn’t fit in my space for large plants in Kratky

For nutrients in Kratky - there are three ways that I would recommend going about it:
1. Pre-mix nutrient solution (for example in a gallon jug), and refill it using that. You'll want to pour out the leftover nutrient solution every once in a while before you refill, since everything that the plant doesn't use will settle at the bottom. (at least with Kratky, since there is no moving water to mix it up like in DWC)
2. Refill using only plain water, and use a PPM meter to determine when to add more nutrients.
3. Have two of the same container - and instead of refilling, fill up the second container with nutrient solution to the half-way point, and move your plant over to the second container. Then you can clean the first one out and reuse it for the next refill. This is most commonly done with 5 gallon buckets, but I've done it with mason jars as well. The only type of container this does not work for is any container where the roots can get bigger than the opening (for example, if you are growing in a gallon jug)

Alternatively, if you use a big enough container, then there is no need to refill it with nutrient solution at any point - one gallon is the perfect size for lettuce, and a radish plant uses less than half a gallon.

[maskedsonnet]

Thank you for the info!! That helps me a lot for planning down the line!

[veng1]

I have a Sprout and an AeroGarden Classic which is intended to use the old very short pods.  The Classic appears to  work more or less with the new longer pods although they don't really fit properly.

So like any self-respecting engineer, I decided to design my own version of an AeroGarden.  However, lacking a current AeroGarden that uses modern pods, I can't measure the proper levels for nutrient.  Which leads me to the following two questions:

Where should the maximum nutrient level be filled to with relationship to the rounded part at the top of an AeroGarden pod?  Clearly filling all the way to the top will not allow any room for air roots.

Where is the minimum level of nutrient with respect to the bottom of the pod?  I'm using a pump that directs the nutrient to the side of each pod similar to what I see in the Classic and an air stone.  My guess is that there is not really a lower limit other than leaving enough level to make sure the pump doesn't run dry but that might allow too much of the roots to dry out.

Summary of questions:

Ideal maximum nutrient level?

Ideal minimum nutrient level?

[lynnee]

Hi veng1!

Maybe this information will help with your project.

Inside a Bounty, the "Fill to here" indicator sits 1-3/8" below the top surface of the grow deck.

When a pod is inserted, the top sits about 1/8 to 3/16" inch above the top surface of the grow deck.

Thus the upper 1-1/2 to 1-9/16" of a pod should remain out of the water. Some experimentation should get you to the right figure. I can't think of any way to tell where the water hits on an inserted plastic pod.

To make a guess about the minimum level, I'd have to measure the distance to the water when the magnetic float is indicating a low water level, and that's not easy to do. I top off my gardens when the water goes maybe a maximum inch below the "Fill to here" indicator. I usually top them off sooner, because the plants like to keep their non-air roots covered.

[veng1]

Nov 13, 2022 17:26:59 GMT -5 lynnee said:

Hi veng1 !

Maybe this information will help with your project.

Inside a Bounty, the "Fill to here" indicator sits 1-3/8" below the top surface of the grow deck.

When a pod is inserted, the top sits about 1/8 to 3/16" inch above the top surface of the grow deck.

Thus the upper 1-1/2 to 1-9/16" of a pod should remain out of the water. Some experimentation should get you to the right figure. I can't think of any way to tell where the water hits on an inserted plastic pod.

Hi lynnee,

Thanks for the numbers.

I'm trying to base my plan on where the water level should be with respect to the top of the rounded hole in the pod because my deck may very well be different from an AeroGarden deck.  I think what you are saying is the water should be about 3/4" below the top of the rounded hole.

I've been doing my measurements by installing an empty pod without a label and either peeking inside or reaching in with a metal tape measure.

I am currently targeting the water pump to stream the water directly into the rounded hole in the pod although conceivably the water could stream onto the solid part of the pod and run down the side into the slot.  I doesn't look like that is how the Classic works but that is a very old design and there may have been improvements since then.

Thanks again!

[lynnee]

veng1, the newer models (Bounty and Farm models) have 2-layer decks that circulate water inside the deck to openings just below the deck surface at the side of each pod hole. (The deck layers snap together and can be taken apart for cleaning.) The water is aerated as it drips from the inner deck to the bowl reservoir below.

The older models have an aerator stalk that pumps water up in a fountain to aerate and circulate the water in the reservoir bowl.

In either type of Aerogarden, the sponges inside the pods are kept wet by drawing up water from the surface of the water in the reservoir bowl. The sponges are moistened from below, not from water that drips onto the tops of the sponges.

There are other members here who are more knowledgeable about the technical side of hydroponic gardens than I. Perhaps some of them will chime in.

[veng1]

lynnee ,

I understand how the newer models work as I've seen some Youtube tear-downs of the inside of the desk.  The channels and small spouts that drip water down the sides as you say.  Consequently, I've designed a deck that functions similarly in that water is pumped into a custom designed, 3D printed deck that also channels the pumped water to the side of the pod.  Again, this is from Youtube and an antique AeroGarden Classic.

Because the sponge is always being continuously wet by the pumped water, can the water level go below the bottom of the pod without killing the plant?

The reason this is of some concern is how long I can go on vacation and expect to have plants alive when I return.  By my rough guess, there are around 2 gallons of nutrient below the bottom of the 6 pods before the pump starts sucking air. 

If the roots are sufficiently developed, say a couple of inches, the system would conceivably go into DWC. Or Kratky maybe.

[lynnee]

veng1, the water level can go below the ends of the plastic pods once the roots are fully developed and extended into the reservoir. (See the diagram at the beginning of this thread.)

Now you're talking about the size of your water reservoir. A Bounty holds 1 gallon of water, and will generally sustain plants for a couple of weeks without refilling. How long the water will last depends on how large the plants are, how many there are, and what kind of plants they are.

Fruiting tomatoes and cucumbers use a lot of water.

Many AGs have a "Vacation mode" setting. It lowers the light level, and (I think) also shortens the hours of light so that the plants will grow more slowly and use less water.

There's no guarantee that your hydroponic plants will survive a vacation, but the beauty of an AG is that it's so easy to start a new garden if an older one fails!

[veng1]

lynnee,

That's very good information.  A two week time frame would be more than enough.

I will have to monitor the water level changes for the different plants when I get further along.

The deck with the channels to direct the water is quite difficult to print, so I've only a 3 containers going right now.

[lynnee]

veng1, please note that I corrected an error in my previous post—a Bounty holds 1 gallon of water. It is a Farm that holds 2 gallons.

[veng1]

lynnee,

Not a problem.  I have spreadsheet I created with the volume of all of the different AeroGardens along with the number of pods and the wattage of the LED panels.

I'm, in concept, designing around a Farm basin but with fewer pods as my opinion is the spacing on the pods is closer that I'd prefer.

I'm currently growing things in a DWC approach with air stones.  The air stones seemed to cause the plants to grow far better but I feel like that I'm forever adding nutrient or water.  I use a Bluelabs Truncheon to check the EC levels and have to add more plain water to keep the EC where I think AeroGarden recommends.  I target about 1.6 mS although Dr. Kratky seems to recommend a little less.  So a thirsty plant with air stones causes the EC to drift up which is exactly the wrong direction.

All this is to say that I want more water per pod.

Some of the DWC designs are published here: www.thingiverse.com/veng1/designs

[lynnee]

veng1, thanks for the link, as I do have a 3D printer!

Some of the members here have experimented with Deep Water Culture. I'll see whether I can find a link for you.

Unless you're really committed to your current design-your-own project, it might be easiest to purchase an AG (a Harvest or a Bounty), and then measure how the nutrients behave when you follow the basic
Instructions.

In my experience, the AG is very forgiving of levels of dissolved solids and of pH levels, as long as you change out the water and nutrients every two weeks.

[lynnee]

Some recent DWC links for you, veng1.

aerogardenaddicts.com/post/50914/thread

aerogardenaddicts.com/post/42118/thread

Here's the basic Kratky introduction, which includes some discussion of nutrients.

aerogardenaddicts.com/post/38290/thread

Wish I could be more helpful, but after a period in which I did a lot of testing for pH and dissolved solids, I decided that my stuff grew fine in the AGs without a lot of extra attention.

Monitoring pH helps with strawberries, but they aren't a very satisfying thing to grow. They attract gnats, and they don't produce a whole lot of berries.

[veng1]

lynnee,

In watching the Sprout and the Classic AeroGardens along with the results of the dozens of things I've printed depicted on my Thingiverse page, I fully agree that the AeroGarden approach works very well.

However, I spend too much time monitoring nutrient levels and EC measurement and want to reduce this maintenance time.  My thinking is that I need to increase the ratio of water per pod.  And one way to do this would be, of course buy a Farm and only fill every other hole.  This would give 6 pods per 2 gallon basin.

A Farm half filled is a rather expensive solution, so I've designed a DIY system that uses a slightly more than 2 gallon container that costs $2.99. 

Then a 3D printed lid that acts like exactly like an AeroGarden lid that allows water to be pumped to each pod.  I can't estimate a cost on that terribly closely but it is only a few dollars in filament cost.  Let's use a big number: $4.

Then a small USB water pump.  Watching carefully on Amazon, say $8.

I don't like 120VAC running in water so the pumps are driven by USB.  A 5 plug USB charger is about $4 per pump.

I'm using LED lights that cover an area of 3ft X 4ft at a cost per tote of roughly $25 each.

In the area of 3' X 4', I'm placing 4 containers with a total of 24 pods.  Consequently, that seems far less expensive than buying two Farm 24s and half filling them.

But truth be told, I'm not doing this because of cost,  I just enjoy designing my own things.

[lynnee]

Nov 15, 2022 10:08:41 GMT -5 veng1 said:

But truth be told, I'm not doing this because of cost,  I just enjoy designing my own things.

Somehow I thought that might be the case, veng1!

You have the situation well in hand, it seems. I love my Farms, but I wouldn't recommend purchasing them if you're more interested in experimenting with hydroponics than in having a very low maintenance indoor garden. The Farms are very expensive (even when discounted at the AG site), and they have to be taken apart if they develop problems (although AG is good about shipping replacement parts while the products are under warranty).

FWIW, I don't understand why planting a Farm with a pod in every other hole would solve nutrient issues. Nutrients are managed according to their concentration per gallon (or other volume) of water.

Generally it's best NOT to plant an AG with a pod in every hole, because the plants end up too crowded. With my Farms (which I've used for tomatoes, peppers, fairy tale eggplants, celery, strawberries, and cucumbers), I usually end up with 2 or 3 mature plants. (Strawberries and celery can be planted in every hole, but I won't do it that way if I try them again.)

The plants need room for roots, foliage, and air circulation if they're going to produce well. My solo Farm eggplant produced as many eggplants as my two Farm eggplants. (Incredibly, those two are still producing after some 14 months!)

Your DIY Farm system sounds fascinating, so I hope you'll post some photos! We all love to see photos of what others are doing.

[veng1]

Well lynnee, my opinion is that the more nutrient volume per pod, the less often one has to add either water or nutrient.

Than opinion is based on what I see from the 3D printed stuff and my AeroGarden Classic in that if one just keeps adding nutrient, the EC levels increase steadily until it is way too high.  My conclusion if the plants use water faster than the dissolved nutrients and a larger container would mean more water available before adjustment is needed, typically adding water.  Please recall that one of my goals is to reduce maintenance tasks like adding water.

I understand that AeroGarden recommends periodically dumping the nutrient and replacing it with a fresh batch but I think that could be extended if one measures the EC levels and adds either water or nutrient solution appropriately.  Naturally, the concentration of the various minerals in the nutrient solution will eventually get to the point where either specific chemicals need to be added or it is time to dump and replace.   The AeroGarden nutrient is cheap enough that my plan is to just periodically dump and replace but I don't know how often that needs to be done if the EC levels are maintained.

Do you know?

[lynnee]

veng1, your plants produce byproducts as they use the nutrients. As these build up, the water becomes more unhealthy for the plants, and the roots start turning brown or black. Changing the water in the bowls eliminates much of the problem.

You do add water periodically to your AGs to keep the bowls topped up. And you are correct that you don't just keep adding nutrients without water or the level of dissolved solids will go too high. The nutrient-to-water label recommendations are calculated for generally good plant growth.

A problem with the Farms is that you can't pump all of the water out of the bowls with the built-in drainage system. My eggplants have been doing fine without complete R&Rs, but my strawberries hated having anything but fresh water.

I'm not one to dispute anyone's personal experiences with hydroponic gardening, but my own experience is that the number of planted pods doesn't have much to do with the nutrients. I do add more nutrients between R&Rs if the plants are heavy feeders like cucumbers and are showing signs of deficiency.

You sound like a "Kratky" gardener to me! Have you seen this great video produced by Dr. Kratky himself? It's interesting as a window into how he thinks. The Kratky method is the lowest maintenance method that I know of, but it still requires refilling the nutrient solution.

aerogardenaddicts.com/post/52660/thread

There is no one answer to how often you need to change the water or add nutrients. It depends on your plants, your water, your light, your room temperature, and your overall growing conditions.

[veng1]

lynnee,

It's not my plan to do Kratky although I have studied that approach.  Dr. Kratky has his own Youtube channel that is quite interesting.

My intent is to design something similar to an AeroGarden with air stones and more automation to monitor EC.  I currently have 4 basins of around 3 gallons each and have 6 AeroGarden pods in each one.  I will eventually go to 8 basins and if warranted, re-print the lids for, say, 8 pods. As I said, I believe 6 pods per 3 gallons of nutrient will need the nutrient changed less often than a Farm with as much as 12 pods per 2 gallons.  These are located in a home brew grow tent on a screened porch and I don't find it that much fun to go outside in close to freezing weather to check the EC levels with a Blue Labs truncheon.

So I've sketched up a design and ordered parts to remotely monitor up to 8 EC levels with temperature correction as EC drifts with temperature although if the temperature changes much in the grow tent, then my temperature controller isn't working correctly.  I'm designing my own circuitry as solutions like Atlas Scientific are way to expensive for multiple probes.

I understand and agree that the nutrient needs to be flushed and replaced periodically.  Do you (or anyone else) know what to measure to identify when the salts get too high? 

I'm thinking that simply measuring EC isn't the answer. pH shouldn't change too much as the AeroGarden nutrient is buffered.  Another possibility is TDS but I don't know if that is the culprit.

I can say that in my plants monitoring EC and setting an alarm to tell me that there is a problem would be a huge improvement as I do a poor job of monitoring those levels manually.

[lynnee]

That's an ambitious plan, and it sounds like you're going to end up with a terrific setup, veng1! Do keep us posted on how it all works out! We love photos, if you have time for them.

The only way that I know of, to tell when salts, etc. are too high, is to look inside the water reservoir for evidence of crystals or brown sediment at the bottom. You can also inspect the roots to see whether they're turning brown or black and getting mushy.

But I'm a "pay attention to what your plants are trying to tell you" gardener. There are others here who are more scientific than I am in their approach to Aerogardening. Perhaps some of them will have a better answer than mine!