Episode-2547- More on Hydroponics — 24 Comments

  1. Hi Jack,

    I’d be happy to talk live to answer many of the questions you had in this episode, especially those related to my long post for the previous Kratky episode.  Fair warning, I’m the dude who wore flip-flops to the workshop and drank most of the host gift I gave you 🙂 .  Just can’t do another long post right now, with my nit-picky proofreading, looking up links etc. that post took 4hrs and final edits at 1am were sloppy AF.

  2. Well THAT post sure reads “bitchy”! Maybe I should skip tonights dinner with clients. 🙂

    I’ll do a play-by-play post to this episode eventually, but let’s talk for faster follow-up.

  3. Jack, I will finish this episode later but I had to leave this comment before I went to bed. I think this is going to be really good.

    Barbera Sher, calls people like that “Scanners” her book “Refuse to Choose” is a workbook to help people manage their unique non specialized nature. I to binge, or obsess on a subject. My favorite teacher in the 5th grade Mr Ferguson was my first introduction to obsessing, because we would deep dive a subject all day or several days until everyone got it.


  4. Thanks Jack for doing a couple episodes on this – I’m excited to try this.  I stopped by my local Indoor Grow Store (that’s the name – Say What You Do and whatnot) but unfortunately the smallest net pots were 6″, and only 25L or 50L bags of clay pellets.  Need to double check the price vs. Amazon for the 10L bag.

  5. Hey Jack I think it also deserves mentioning the use of hydroponics or aquaponics for fodder systems. I know it doesn’t apply to you so much but for those who have rabbits there are tons of examples on YouTube and I have even seen a few articles of commercial level all the way up to cattle, though its generally seen as less efficient than buying bales. One of the better analysis I have seen


    I think this could seriously make the difference for indoor rabbitries at the indoor or homestead levels using wheat/rye, alfalfa or sunflower. I had not touched hydro or aquaponics due to finances and it felt somewhat intimidating to be perfectly honest but I think I will be doing the kratky method soon.

    • Also as I look at Kratky for the production it seems less expensive then anything but strait in ground gardening. By that I me a climate that requries little to no irrigation, is already fertile and doesn’t need something like raised beds.

    • Very interesting and it doesn’t surprise me but it does make me wonder.

      So he grew in a pot tent, which is good for variable elimination but it does make me wonder about kratky outside which it seems best for. The temps outside during a growing season are going to warm a cool with a lot of varience. This is going to have a marked effect on humidity inside the container. ie Evaporation, condensation and falling back into the solution. This would be even more true in say a tropical climate (Hawaii where it was developed). Simply put solar radiation is going to have a much bigger effect on this than a grow light. Given Dr. Kratky developed this for use in poor areas using zero energy (no lights) it may simply work better that way. I may try like a pepper and tomato both ways outside this coming season. Just to see.

      The most interesting thing is seeing the plants move ahead of the light! This lends some consideration as to why fish tanks that are on timers have less issues with algae then those people manually turn on and off even when said people are reasonably consistent.

      • Also this makes me think may be (again MAY BE) with kratky you may want to fill a bit higher than many recommend. Why?

        Okay it is clear the kratky one air pruned, had those side roots initially contacted water they may have continued to chase it. What is cool is how easy this is all to test.

        • Hmm exact opposite result but I am just betting that small container under a much higher heat producing light, got more humidity to the roots.

  6. Yes, the time lapse was very interesting!

    The take away for me was the aerobic conditions of DWC vs the possibly somewhat anaerobic conditions of Kratky and how different plants will respond in those conditions.

    Good point on the higher initial water levels!


    • Hey wanted you to see these, not on Amazon and I am sure that the cost would be high if they were.

      Saw them at Lowes, they will likely go on sale right after Christmas when all the storage shit does. I know you are happy with your 3.5 gallon buckets but you may want to look at these if you plan to expand. They are VERY rugged, and squat compared to a typical 5 gallon bucket. Also not much more when you factor in you have to buy a lid for buckets and these come with one.

      I have decided to use the 5 gallon rectangle ones of the same line for my first experiments, that is these guys.

      Gotta say right now my struggle is not designing a fricken small scale commercial system! So fricken easy to to.

  7. This is very interesting.  I’ve always read that the biggest advantage of Aquaponics over Hydroponics was the absence of salts.  It is/was my understanding that Hydroponics has a build up of salts as the nutrients are used up from the water and you had to deal with that “salty” water (as in it couldn’t go into your regular garden after use, even to the point of commercial hydroponic growers having to treat their waste water in a fashion similar to industrial waste disposal).  Maybe because this method doesn’t suffer from that salt build up because of rapid turnover? lack of nutrient replacement? or maybe my understanding in flawed.  But this makes a ‘condo’ or patio garden more realistic for food production in my opinion.

  8. Loved the bit on the being a Polymath.  I’ve been self-employed in industrial automation for the last 8 years, before that as an employee for about 10.   I’ve had numerous job offers but can’t make myself go back to being an employee because there always seems to be a cap on what you can learn before you become essentially bored with it.  I think this is called ADD in government schools.  My son is somewhat the same way and is one of the main reasons we homeschool.

    Hunting, long drives or trying to watch TV is hard because my brain can’t keep up with the ideas going through.  I have a document on my phone named Brain Dump, that I try to record as much as I can.  I tried writing notes but got to the point I couldn’t write fast enough and my handwriting ended up looking like a doctors signature and later couldn’t read what i wrote.  There are times where I have went back and even replayed in my mind what I was just doing to try to remember what I wanted to write.

  9. Hi Jack,

    Been enjoying the excitement about Kratky method.  It is interesting in that it reminds me of a number of ideas I’ve had and implementations. (Way back in high school, in our marine biology class, we were tasked with creating a balanced ecosystem inside a closed 2 liter bottle. While most only tried to include plants, I’ve always prided myself in that I successfully incorporated animal life – including a few small amphipods. A couple months later, I could still see a few amphipods swimming around.  That is until a paint crew moved all of our bottles right in front of the big window facing the harbor. We came back after the weekend to pretty much find all of our bottles nothing more than boiled algae blooms.)

    About 2 years ago, I tried the soda bottle + beta fish + plant atop.  The two fish with basil plants succumbed within a month or two, but my youngest’s with a mint went on for nearly a year. And if she had changed the water as instructed, might have gone longer.  However, the plant is still growing in that 2 liter jug and is now approaching year four.  When you described the Katky method, I thought of the similarities. Roots go from top and down to bottom. I periodically replenish the water.  But some roots always receive air, and they never fully dry out. The top is very narrow and retains moisture.  I also have lemon grass I bought from a store that is now 3 years old.   I am thinking of re-purposes juice bottles as planters in this fashion for  window herb garden. And then once my aquarium is back up, simply watering them with the nutrient rich tank water.

    Further thought on Kratky and non-moving parts. Pondering the idea of running wicking material from a a water filled jug to each plant, perhaps running the wicking material thru some plastic tubing. Then I could just dump water changes into that one jug.  I don’t think the wicks will provide enough moisture, but I am curious,  if a plant consumers more water, it will make it’s semi-closed environment dryer, thus potentially pulling more moisture from the wicks.  And hopefully, providing enough moisture that if Jason forgets to check and add water, the plant won’t dry out.

    More recently, a friend acquired a large bunny. Thing reaches my waist when standing up.  Greens are a much consumed substance. And I have been thinking of putting into implementation an idea I’ve had for several years.  Which is to make use of the PVC drain pipes with the pre-drilled holes.

    See photo:

    The idea is to cap each end and suspend it.  During the winter, I could bring it inside, hang it from the ceiling, along with some grow lights. During the summer I could just hang it from a tree limb.

    – no weeds to pull.
    – minimal watering and evaporation
    – could potentially create a simple auto-watering system, similar to the pet bowls that use a 2 liter bottle but only fill up to the rim of the bowl, to perhaps ensure the very bottom always has centimeter of water
    – two people can move easily for relocation inside during the winter
    – easy to suspend growlight from hanging chains (though I am actually thinking it may be better to have the grow lights on the side.  The plants will naturally grow upwards to reach the natural sunlight, and grow lights on the side may lead them to bush out much more
    – easy to identify each plant since each hole would equate to a type of plant
    – for lettuces and greens, I think this system could provide my friend with a fair supplement for her bunny companion and save lots of money expended purchasing greens at the grocery store during the winter.



  10. I have had this pump running continuously since 2012 on my IBC AP system.  The system is in my shop so I clean the dust out of the intake filter every so often.  I’m using it with 3 air stones and have replaced those a couple of times.

  11. I have one outlet capped. 2 go to air stones in the fish tank and one goes to a bathtub grow bed that’s sitting off to the side. That one is hooked to a hard plastic tube that’s just pushed down into the media (pea gravel). This bed is a little different in that the top height is only slightly above the water line in the fish tank so I can’t do a flood and drain. It runs constant flow.

    Hopefully I can explain the drain on it. The drain is out of the old tub overflow hole towards the top – where the drain lever goes. A 1″ PVC pipe comes through a uniseal in this hole and connects to an elbow. The other end of the elbow is pointed straight up. A 3″ PVC media guard is around this (the outlet tube runs through it). The media guard is slotted along the bottom.

    The idea is that the water flows in around the top, travels down through the media, through the base of the media guard, up, and out through the open top of the elbow. I was a little worried about stagnation at the other end of the tub so I added the air line to keep some oxygen going in that end.

    There are 2 $18 Harbor freight 264 GPH pumps in the system – one to the tub bed and the other to the IBC grow bed (top 10″ of the IBC flipped over). This system has been running well since 2012.

  12. Love the idea of kratkey. I’m just starting to explore learning about out of ground growth options. You mentioned adding fertility, like for long term nutrition as in a hydro system, but doesn’t this system just hydrate the roots by evaporation and humidity? I’m under the impression that evap. Is like a distillation process and it doesn’t seem that the nutes will be available in the ‘mist’. Will they?

  13. Heads up, another link laden post coming right after this, I’m assuming it will get tagged as spam.

  14. OK doing this in two parts.
    Part 1 responses to Jack’s show notes.

    -Rapid, obsessive, learning:
    Completely agree, and that’s exactly how I operate. It has served me well professionally and personally. It’s my standard MO so hadn’t thought much of it until my Son pointed it out one day. Kid is more observant that I thought, maybe he is finally outgrowing his boy-tardation. 🙂

    -For Seed Starting:
    Regular Kratky and similar wicking-style options like rafts work well for seed starting. I’ve use 40 and 60 cell models of the raft and plug/sponge based Park Seed Bio Dome seed starting systems for years with great success. My only complaint is the brittle plastic used for the dome lids, they will crack if dropped from waist height on a hard surface. Other than that, Bio Domes are sturdy and reusable, I’ve had mine for 6-7 seasons without issue. The base for example is more pliable, I haven’t cracked one yet.

    Note: This section is mostly applicable for starting fairly small seeds like tomatoes, lettuce, herbs, etc. I’ve found plugs/sponges to be unreliable for plants with larger seeds and/or especially sensitive to transplant-shock like cucumbers and melons. I’ll address those further down.

    Now for the links. Except where noted like the Park Seed Bio Domes, I do not use these exact products, just listing here as examples…

    Park Seed Bio Domes. I like the 60cell units due to the lower cost of refill plugs/sponges.

    Park Seed starting refills: I use the smaller 60cell refills for almost exclusively. Even if they fit loosely in my 40cell Bio Dome, or 72cell 1020 trays, they are rigid enough to stand upright in the larger cavities and work fine, even for larger plants like tomatoes. If you buy 2+ of the 120pk refills the price is $17ea, or about 15cents per plug.

    DIY options include industry standard 10in x 20in a.k.a. “1020” tray flats + seed starter trays + humidity domes + grow media like plugs, rock wool, or potting mix. Your local hydroponic store is your friend for these supplies. Big box stores are way overpriced by comparison. Amazon links included for convenience…

    5pk of 1020 tray flats, plenty of similar options on Amazon etc. NOTE: These *DO NOT* have drain holes! In this case you do not want drain holes. Double this check if you order alternatives.

    5pk of 72 cell 1020 seed starting trays. Note: Cell count options range from 24 to 288. More cells = smaller cells so choose accordingly to match your plants. I pretty much only use 72 cell setups so only listing those in this post.

    5pk of tall 1020 humidity domes with adjustable vents:

    2pk 1020 kits with flats, 72 cell starter trays, and humidity domes if you prefer kits: 2pk kit with flats, 72 cell starter trays, and humidity domes:

    100pk grow plugs:

    98 cell sheet of rockwool example, there are plenty of other cell count options. These are drop-in perfect for 1020 tray flats. Tip: Break out the corner cells so you can monitor the water/nutrient level. Keep the level low, say a ¼” of standing water and when needed refill via the open corners, i.e. “bottom fill” do not “top water”.

    Caution regarding rockwool: Rockwool WILL spike up your PH levels making for a far too alkaline (like 9+ph) grow medium and sucky results. Be sure to pre-treat rockwool with a “PH Down” product or other means of acidifying your water to 5.5ph. This only needs to be done once and should result in a fairly neutral ph grow medium.

    For larger seeds, transplant-shock sensitive plants, or plants you simply prefer to grow out a bit before transplanting, use the “grow bag” method:

    Use 32 cell 1020 trays like these.

    Then fill cotton bags like these (I use this specific vendor’s 4×6 bags) fill with potting mix and stand them upright in the above 32 cell trays. Basically use them as inexpensive, bio-degradable “grow bags”. Start your seeds in these bags and transplant/bury the whole bag in the ground or container when ready.

    It is vitally important you keep these particular grow bags as sterile as possible prior to transplanting! The fabric is thin and will degrade quickly if fungi is allowed to propagate. You’ll end up with a clump of potting mix and no bag in a matter of days. Use some H2O2 in your nutrient mix to keep the bags intact.

    Conversely, I recommend giving these bags a nice dunk in mycorrhizal fungi inoculated water just prior to transplanting. This ensures the bag will degrade, removing it as a root barrier, and gives your plants the benefit of myco fungi and better nutrient absorption. I use Great White for mycos and other beneficials. Link for the 1oz, it gets less expensive per oz as you buy larger units

    You could also use more durable cotton or burlap bags, but my wife bought a 100pk of the above for gifts or something, so I’m making do with these for now. Just make sure the fabric is not some type of natural and biodegradable material .

    -Tips/hacks for seed starting:

    First a few words on why these various wicking-style methods (Kratky, raft, plugs/sponges in shallow standing water, or grow-bags) work so well. It’s all about moisture control. The seeds get adequate, steady, moisture without drying out or drowning. Always water from the bottom, never pour water on top of the seeds!

    Start with a sterilized/sanitized growing environment. My preference is food grade hydrogen peroxide (H2O2). Do not use the 3% stuff from your local drugstore. It probably contains some form of stabilizer chemical. Buy real 33-35% food grade H2O2 if possible, rather than the pre-diluted 12% stuff you’ll find on Amazon. BE CAREFUL with high concentration H2O2! Wear protective gear and dilute the stuff with distilled or filtered water before using. 3-6% H2O2 is good for deep cleaning/sterilizing pre and post season.

    Use H2O2 for improving seed germination rates and speed, increasing seedling vigor, and generally keeping pathogens at bay. I use it to pre-soak seeds (1-3%), in my seed starting water/nutrient solution (.25-.1%), and in a spray bottle for misting seedlings, humidity domes etc. (.5-1%). You can google yourself into a rathole with uses of H2O2, and much of it is “woo-woo”, but this is a good science based place to start…

    Side note: H2O2 is fantastic for micro-greens and edible sprouts, use at about .5-1% concentrations and you will have zero mold problems.

    Add some salicylic acid (SA) a.k.a. aspirin to your pre-soak and nutrient solutions. Yes it works, seems people used willow bark back in the day, but the benefits were largely forgotten, by me anyway. SA use can benefit seedlings and mature plants. It works best via the roots, less so via a foliar spray in my experience. It has worked for my tomatoes, reducing blight from a 100% certainty to about 50%, meaning half my tomatoes never got blight this year, and those with blight were able to produce at near normal levels. I use regular, cheap unbuffered, uncoated store brand aspirin at 250mg-500mg per gallon of water. Again, lots of “woo-woo” if you google, but start with some science ….

    Do yourself a huge favor and start with an all-in-one premixed nutrient concentrate from The Urban Farm No need to blend your own concentrate or do any math regarding ratios of base nutes vs calcium/magnesium blend. Just add their concentrate to water, and dial-in to the proper dilution as measured with your EC meter.

    -The process:
    Start seeds under sterile conditions in closed humidity domes with very little (0-10%) nutrient in the solution, plus H2O2 and SA as outlined above. Note SA will accumulate/concentrate due to evaporation, so use at 250mg or less per gallon. H2O2 breaks down into water and oxygen, so there’s no issue of accumulation. Fill your trays as appropriate for your chosen method, quite full for the Bio Domes, and quite low for everything else, and bottom water to maintain levels. Cheat: I kinda break my rule against top-watering to kick things off. Once I get seeds situated in whatever grow medium I’m using, I use an eyedropper with SA and 1-3% H2O2 and place a few drops right on top. I do this instead of a separate pre-soak. Mist the interior, including baby seedlings, periodically/daily with .5-1% H2O2 to maintain sterile conditions

    Start more seeds than you need. I usually start 2-4x what I really need as “backup” plants, a bit of an insurance policy in case I accidentally drop or otherwise kill a few seedlings. I share any excess with friends, family, or neighbors.

    Use plant labels or stake tags! Stick them right in the individual cells or end of rows. You will need at least 2 tags per plant variety. One for the seed starting tray, and one for the transplant tray below.

    I do use Jack’s recommended 45W Kingbow lights. 1 Kingbow per Bio Dome, and 2 per 1020 tray. They work great, and you can drop them very close to seedlings without burning leaves.

    Use some form of heater for the starter trays. I use standard 1020 heating mats like this

    Soon after sprouting move seedlings to clean, previously sanitized but no longer sterile, 1020 trays with open vented domes or no cover at all. Less cover means less humidity and less chance of damping off issues. Do not use H2O2 in your nutrient mix here, we’ll want to prepare the plant roots with myco fungi in this stage, and H2O2 will kill the fungi. So add some myco fungi to your nutrient solution, you can keep using SA if you want. Do continue use .5-1% H2O2 to mist the tops of your seedlings. Be careful to mist lightly, we don’t want H2O2 seeping down to the roots. Fill and maintain the transplant trays at no more than ¼-½ full of nutrient solution, lower is better.

    A 50% nutrient solution is a good middle-ground for transplant trays, promoting a bit more aggressive root growth than a more concentrated solution. Adjust up or down according to your goals and plant response. Ex: For tough stocky plants, starve them a bit with 10-25% nutrient, use intense or up-close lighting, and keep the root zone cool/cold. To hold longer and/or grow-out completely use 100% nutrient and appropriate lighting and warm the root zone if needed.

    Note the transplant tray is basically a fully functioning hydroponic setup, you can grow good sized plants here if you want. I’ve held my backup tomatoes for months past transplant time in such trays. With proper lighting, they actually set and produce fruit faster than my outdoor transplants

    Grow out the seedlings as desired, then harden, and eventually move to their final destination. Do give the plants a good dunk in fresh myco inoculated water during the final transplant.

    -Where and why I may go beyond Kratky:
    Air pump for seed starting: Not necessary for actually starting seeds just use H2O2. You get “aeration” as it breaks down into water and oxygen, plus maintain sanitary conditions. An air pump is of questionable benefit for transplant trays, but good or full on hydroponic growing. Air in a raft-style system is fantastic for propagating cuttings.

    -Almost Everything you Need for Kratky Hydroponics:
    EC Meter: I have used the HM Digital AP-2 years, it works great.

    Not mentioned but a PH meter is important for some plants like tomatoes: I’ve used the the Oakton pHTestr 20 for years. Seems to have been discontinued and replaced with the phTestr 30, runs $100 on Amazon. Oakton has a good reputation, if a bit pricy. They also have a more affordable EcoTestr line, EcoTestr pH 2+ runs about $60.

    Also not mentioned regarding PH: Use PH Up/Down to adjust per recommendations for the plants you’re growing. Note PH tends to go up naturally as plants grow, so you will eventually need more PH Down than Up, but start with both…

    Texas Tomato Food: Yeah the shopping cart sucks! You can buy a mix-n-match case of 4 1gal concentrates, but the process sucks. Buy any 4pk case, then reply to your confirmation email with the specific mix-n-match you want.

    3.5gal buckets: The same company, Agee, also makes 5gal buckets. These are nice heavy-duty buckets. I buy the black ones to block light, then paint with a light color to reduce solar gain. These are also 10pks so only $2.80/per bucket.

    4 Way Air Pump: I use the linked product and it has been running 24/7 utterly neglected outdoors for 3-4yrs years now without issue, except when I allowed it to flood due to rain last year. Actually, it ran fine, but kept popping the GFCI breaker. I literally dumped out the water, plugged it into a non-GFCI outlet, and let it dry itself. Mine runs 1 large, fist sized, air stone in a 55gal drum (my main hydroponic tank) and 2 smaller stones in a pair of makeshift 1ft deep raft containers. Being able to dial-down airflow for each port has been super handy, this thing blasts a ton of air for such little power consumption. It’s also pretty quiet. I did purchase a set of replacement diaphragms to have on hand for the eventual failure of the original set.

    Part 2: Responses to podcast audio not already covered above:

    41:25 Humidity domes, tall vs short: I recommend the tall ones with vents unless you have tight height restrictions. The tall ones are more flexible because you can start seeds of course, but you can also grow out plants longer under protection, but with the vents open, less chance of damping off issues. Regarding mold, just mist the plants and lid with diluted H2O2 as outlined above, no mold issues.

    42:15 EC Meter: EC meter use is very easy and much more accurate than eye-balling with some number of ounces per gallon recipe. You’ll also have no idea what your true nutrient levels are as plants consume them over time. Dial-in exactly per your nutrient manufacturer’s instructions, then remeasure and top-up as needed over time. Ex: Texas Tomato Food (TTF) instructions recommend 1.6 (1600 on the meter) for seedlings and 2.2 (2200 on the meter) for mature tomatoes. Those numbers are in addition to your baseline water readings. My source water reads ~700 on its own, so I would add TTF until I hit 2300 and 2900 respectively.

    56:19 Shelf life of nutrients: Solid nutes do have a practically infinite shelf life. However I have had some of the pre-mixed stuff from TTF folks for 2+yrs and it works fine. Some of the minerals do settle out into little chunks over time, but I just toss it in a blender and let it run for a while, then it’s good to go. Also if you have some left over at the end of a season and have concerns about storage/freezing, just know that it works great in regular outdoor soil. Go ahead and give your trees a treat.

    57:20 Blight: Starting with sterile growing environment combined with SA should help you stave off or limit the destruction of blight. Do add myco fungi and other beneficial biologics to crowd-out the bad stuff. I use Garrett Juice Plus along with the previously mentioned Great White for mycos and other beneficials.

  15. @Olin Regular Kratky starts by using the grow medium as a wick, touching the nutrient solution and bringing moisture up to the seed/seedling. As the plat grows it drinks the solution. Eventually the solution will drop below the wick, but by that time the roots should be in in direct contact with the solution, no longer needing the wick.