Episode-2545- An Introduction to Kratky Hydroponics — 24 Comments

  1. Jack, thanks for bringing this to the community! I’ve been interested in aquaponics since you first started talking about it, but the idea of having to f with pumps, pvc, power sources, etc turned me off. So I’ve been gardening in-ground only, but now I can’t wait for spring!! I’m literally pissed that it’s only November. I’ll probably play around with it indoors for the next few months just to learn what I can before spring. Thank you sir!! I have a feeling this is gonna become a big deal with this community.

  2. I’m still listening to this episode. But you keep talking about lettuce, spinach etc. I’ll use Kratky for that, of course. But now I’m thinking about all the shit that could potentially be propagated this way. I’ve had a few beers so may not be totally coherent, but holy shit you’ve got me excited dude.

  3. Hello Jack,

    As my mother says “Growing old is mandatory, growing up is optional.”

    Thanks for all you do.

    Happy Thanksgiving, Merry Christmas and Happy New Year.

  4. For shallow and wide containers, perhaps looking at bins that are made to fit under the bed. Though at a certain point, wide and shallow and full of fluid would be awkward to carry.  You’d start a wave pool in your hands.

    • The one key is you don’t want to be too shallow. First you want to start with head space just about 1/4th of an inch higher then the bottom of the net cup. So depending on the size of the net cup you use that level will vary. Next with Kratky you want the water to last so you need some depth for that.

  5. I’ve mostly used the Kratky method for smaller plants like lettuce, and rooting of tomato cuttings where it works quite well!  Mostly using 3.5-gallon buckets which are ~$4-5 with lids in 10pk quantities from amazon, the build-in handles make these easy to pickup and move as needed.  Also grew some pepper plants in 5-gallon buckets (bigger and cost a bit less than the 3.5gl buckets) with purpose made 6″ meshpot/lids.  The lids are sturdy enough to hold decent size pepper plants without sagging.  A few tips, and more links for Jack…  🙂

    Totally optional but as you might expect, plants do better when aerated.  I have a this 4-port model for my outdoor hydroponic setup.  It has plenty of spare air and ports to supply my nearby buckets.

    I use buckets and lids from this company, VERY thick and sturdy plastic.

    Use this type of lid for larger plants like peppers.  Also drill small holes around the perimeter to hold sticks as supports.

    If you want a simple to use premixed nutrients, I am a huge fan of The Urban Farm products.  Use their vegetable formula for most things and Texas Tomato Food for tomatoes and peppers, I’ve used it for years and the results are outrageous. 

    Note if you buy 4 gallons, go to their web site ( for 4 gallon “cases” and better pricing.  They will do mixed cases BTW, just order a 4pk of one thing, then reply to your confirmation email with the mix you want.  Otherwise Amazon has single quarts and gallons…

    Side note:  If you want a pre-build hydroponic system, and don’t mind paying the price, The Urban Farm makes a ready to use kit.  I’m on my 5th or 6th season and it has held up well outdoors, though I now have a few cracked buckets and will be replacing all of them with the above referenced 3.5gl buckets.

    An EC (Electrical Conductivity) meter is much more reliable tool for measuring nutrient content in your system than “eyeballing” it with X grams per gallon of water.  An EC meter measures the conductivity of your water + nutrient solution in µs (microsiemens), note this is not the same as a TDS (Total Dissolved Solids) meter.    Measure your source water before adding nutrients, use this as a baseline, then add nutrients to hit your target µs reading.  Ex: If your source water measures 700µs, and the nutrient recommendation is 2000µs, you need a final cumulative reading of 2700µs for your plants.  There are plenty of options on Amazon, and the cheap $12-$20 meters work fine.  

    Optional but recommended: Use a PH meter and PH-up PH-down fluids.  I use this one, but see plenty less expensive options on Amazon.  Mine is working fine after 5+yrs, no idea of the cheaper models are as durable.

    If you go with the Mastergrow nutrients Jack mentioned, watch this video and mix up gallon quantities of liquid concentrate.  Liquid concentrates are MUCH easier to use vs mixing per the Mastergrow’s instructions each time you need nutrients.  Note: This guy says to shoot for an EC reading of “2.0” which is another way of saying 2000µs.  He is using RO water which should have a near zero µs reading, see note above regarding EC meters, measure your source water and adjust up accordingly, your target EC reading is cumulative, so source water µs + 2000µs = your target µs reading..

    Check out this guy’s tree sized tomato plants grown in 32 gallon “buckets” (trash cans) and plenty of other plants using the Kratky method.  IMO his big plants would do better with bigger net pots and his indoor stuff is suffering from lack of sufficient light, but good info is provided none the less.  Some of the tomato root mass pics are insane.

    IMO the simplest way to start is with a quart of Urban Farm premix, an EC meter, a small container with a hole  punched in the lid (1/4 inch minimum is a good start though larger tends to be better), and some paper towel as the grow medium…
    –Fill the container nearly full with water, add premix to hit your target µs reading per the premix instructions.  
    –Roll a piece of paper towel into a tube which will fit snugly in the aforementioned hole in the container lid.  
    –Shove/pull the paper tube through the hole until it penetrates the water by an inch or so, allowing it to act as a wick.  
    –Cut the top of the wick to a 1/4 inch or so and stick a seed in the top.  Lettuce is a good test plant.
    –Place the container in a window or use a grow light
    –You’re done, enjoy!
    –Once you’re comfortable, scale up to bigger containers with bigger holes with net pots and rock wool, etc. 

    • Awesome comment a few things….

      1. The reason is was delayed being published is there were so many links it tripped the spam filter and I had to go find it and dig it out.

      2. I got a gallon of that fertilizer even a gallon is a bit less on their site because you pay big time shipping if you get it on Amazon.

      3. Are you saying that you use JUST THAT TOMATO stuff and nothing else in your nutrient, no epsom salt or other addititves?

      4. They stopped making the complete kits just so you know.

  6. Regarding your comment that you cant start seeds in clay pebbles, well I do.
    It is pretty simple.
    Fill your net pots.
    use a spray bottle and spray the pebbles BEFORE you add your seed.
    Then drop in your seed. Since the pebbles are wet the see will stick to a pebble.
    Then twice a day spray the net pot with spray bottle but from a distance so the mist does not
    “relocate” the seed.

    If you set your net pots inside another container, say an old plastic lettuce package then pack the netpots
    with more pebbles around them. Fill the lettuce container with your H2O (I use aquaponics water).
    Use the above method to start the seeds.
    The roots will grow long enough so that when you transplant into your system the roots will actually reach the water level. This is how I start my plants for my DWC raft beds.


    • Sounds like it works but sounds like you would be misting quite a bit. I think capping with something like say .5 inches of perlite would eliminate that need.

  7. Try starting with rainwater for hydro grows. So much easier to adjust ph. And it’s really clean- as far as ppm goes. Mines usually 10ppm. Then you won’t fight the metals in your well water. I didn’t want the chlorine and fluoride in my city water.

    • I am doing a follow up today and that just went in the notes. FWIW most rain water here anyway ends up still over 7 PH, though I bet you are right about it being easier to lower.

  8. 1: I remembered that from a previous link ladened post, no problem, plus the URLs needed editing. 😉

    2: Maybe shipping to Cali makes the price difference a wash for me? $39.95 direct vs $39.99 including shipping from Amazon. Sorry to beat a dead horse, buuut, an MSB discount would be awesome! Ask for Ed at the 281-608-9275 number. 🙂

    3: Correct, this guy’s nutrients are all-in-one. Doesn’t sound possible right? All I can tell you is his stuff works as-is. This thread on dates back to 2013, and where I first heard of TTF (Texas Tomato Food) Ed chimed in a few times over the years with helpful info. FWIW I do use his Veg formula for other plants like lettuce which prefer different NPK ratios.

    4: Bummer. His system got me from zero hydro experience to flawless production on my first try.

    • Oh the MSB hit up is coming as soon as I actually get my stuff from him and verify it. I assume you’d expect no less from me.

  9. You mentioned coming up with a better sustainable growing medium. What about fluffy sponges? You could grow your own. Probably could reuse them a few times.

  10. We use it as an innoculum in aquaponics and as a mineral adjunct there. With hydro while I am new I say no. Hydro doesn’t have any bacterial biology medium, etc. to deal with biologics.

  11. TO save time on drilling holes for 2″ net cups. Try using the Ikea  trash bag holders.

    It comes flat. just need to trim off one end. It will hold 34 2 inch netcups.

    I attach a few (7) inverted netcups on one side as legs to stand up out of the water.

    Perfect size for a bussing tray. Cover with clear plastic with grow lights on top.

    No need for grow tents. Good way to start a lot of net cups at once.

    To begin with, I soak lettuce seeds in water until a small root appears.

    Then fill 2 inch netcup with hydroton and soak to get wet.

    Use a kitchen baster to extract 3 seeds and gently drop on top of hydroton.

    Place the seeded netcups in hole cover the whole thing with clear plastic.

    Set under lights for a week or two. As they develop, transfer to your final growing container.

    Or extend the legs, and add nutrient solution and continue to grow in place.


  12. I forgot to add a few details.

    Once you fill the whole rack with seeded netcups, place it in the bussing tray and fill the bussing tray with enough water to keep the net cups hydrated.

    You can eventually replace the plastic with fiberglass screen to provide a bit of air into the system.

    Keeping it enclosed makes it aphid proof.