No-Pump Kratky Jars & Totes (Easiest Hydro)
Passive hydroponics with zero pumps and zero electricity. You fill the container once, the water level drops as the plant drinks, and an air gap forms for the roots. Perfect first hydro build.
Estimated cost
$25 – $60
Estimated time
30 – 45 minutes
Lifespan
Indefinite — no moving parts
Soil needed
None — clay pebbles or rockwool only
Weight empty
1–2 lbs per jar
Weight full
5 lbs per jar · 200+ lbs for a full tote
Best for
Lettuce, bok choy, herbs, spinach, arugula — fast, shallow-rooted greens
Placement
A sunny windowsill or under a shop light. Keep jars out of hot afternoon sun or the solution cooks.
Boards to Buy
| Boards to Buy | Quantity | What You Use Them For |
|---|---|---|
| Wide-mouth half-gallon mason jars (or a 27-gal tote) | 4 jars | Reservoir — one plant each |
| 3-inch net pots | 4 | Sit in the jar mouth / tote lid holes |
| 1.5-inch rockwool cubes or peat plugs | 4 | Seed starting |
| Clay pebbles, small bag | 1 | Fills the net pot around the cube |
| Black duct tape, panda film, or sock covers | 1 roll | Blocks light from the reservoir |
- ·Hydroponic nutrient (a simple 1-part leafy-greens formula is plenty)
- ·pH test kit or pen, plus pH Down
- ·Distilled or filtered water if your tap is very hard
Steps
- 1Start seeds in rockwool cubes. Keep them damp and covered until sprouts show, then give them light.
- 2Wrap or paint the outside of each jar so no light reaches the water. Light plus nutrients equals algae, every time.
- 3Mix nutrient solution per the label — use half strength for young seedlings.
- 4Adjust pH to 5.5 – 6.2 before filling.
- 5Fill the jar so the solution just touches the bottom of the net pot (about 1/4 inch of the pebbles submerged).
- 6Set the rooted cube in the net pot and surround it with clay pebbles.
- 7Place the net pot in the jar mouth. Set the jar in bright light.
- 8Do not top off. As the plant drinks, the level drops and an air gap forms — that gap is what feeds the roots oxygen.
- 9For a tote build: cut 3-inch holes in the lid on 8-inch centers, fill with 15–20 gallons of solution, and treat it exactly the same way.
- 10Harvest when the reservoir is nearly empty — a head of lettuce usually finishes right about then (4–6 weeks).
- 11Rinse and refill for the next round. That's the whole cycle.
Tools needed
- ·Measuring cup
- ·Hole saw (3-inch) — only if using a tote lid
- ·Scissors
- ·Permanent marker
Common mistakes to avoid
- ·Topping off the water — it drowns the roots by removing the air gap
- ·Skipping the light block, then fighting green slime all season
- ·Trying fruiting crops like tomatoes, which drink far more than a passive jar can hold
- ·Starting seeds directly in the net pot with no cube — they dry out before rooting
Maintenance tips
Wipe jars with a vinegar rinse between crops. Check pH once a week if the plant looks pale. Toss and remix the solution if it ever smells sour or turns cloudy.
Community builds
See how other gardeners built their no-pump kratky jars & totes (easiest hydro) — and share up to 3 photos of yours.
Sign in to view photos other gardeners have shared.
Sign in to share photos of your build.