I started growing hydroponically because I wanted fresh basil in January without paying $3 for a wilting plastic clamshell from the grocery store. The Kratky method got me there for about $12 and 20 minutes of setup time.
If you have heard the term “kratky hydroponics” and wondered whether it actually works or just sounds too simple to be real, I can confirm: it works. I have run Kratky jars and buckets for over a year now, and it is the method I recommend to anyone who wants to try hydroponics without spending real money or learning how to wire up pumps and timers.
This guide walks through everything from the science behind the method to a step-by-step setup you can finish this afternoon. If you are completely new to growing without soil, our hydroponics 101 guide covers the basics. If you already know you want a passive, hands-on method, keep reading.
What Is the Kratky Method?
The Kratky method is a passive, non-circulating hydroponic technique developed by Bernard A. Kratky, a researcher at the University of Hawaii’s College of Tropical Agriculture and Human Resources. Kratky began publishing on non-circulating hydroponics in the late 1980s and formalized the method in a peer-reviewed paper on growing lettuce without any water or air circulation.
The core principle is straightforward. You fill a container with nutrient solution, place a plant in a net cup so its roots touch the water, and leave it alone. As the plant drinks, the water level drops and an air gap forms between the surface and the lid. That gap gives the roots oxygen. No pump pushes air into the water. No timer cycles anything on and off. The plant does all the work.
This makes Kratky the cheapest and simplest entry point into DIY hydroponics. Zero electricity cost. Zero moving parts. The entire system is a container, some nutrient solution, and a plant.
What You Need to Get Started
Containers
Any food-safe, opaque container works. I use quart-size mason jars wrapped in electrical tape for herbs and 5-gallon buckets with lids for lettuce. Mason jars cost a couple of dollars each. Buckets run $3 to $5 at a hardware store. Dark-colored storage totes (10 to 18 gallons) work if you want to grow multiple plants in a single reservoir.
Opaque matters. Light hitting the nutrient solution causes algae, and algae competes with your plants for nutrients and oxygen. If your container is clear or translucent, wrap it in tape or paint the outside.
Net Cups and Growing Medium
Net cups are small slotted pots that hold the plant and growing medium while letting roots grow through into the solution below. Use 2-inch cups for mason jars, 3-inch cups for buckets. A pack of 25 costs $5 to $8 on Amazon.
Clay pebbles (also called hydroton or LECA) are the most common growing medium for Kratky. They are lightweight, reusable, and drain well. Rockwool cubes work too, especially if your seedlings started in rockwool plugs. I prefer clay pebbles because they are easier to rinse and reuse between grows.
Nutrients
You need a hydroponic-specific nutrient formula, not regular plant food or garden fertilizer. The difference is that hydroponic nutrients include the full range of micro and macro elements that soil would normally provide.
I use General Hydroponics MaxiGro, a one-part powder that dissolves in water. A 2.2-pound bag costs around $17 and lasts months because you only need about one teaspoon per gallon. The General Hydroponics Flora Series (a three-part liquid) is another popular option, though it costs more at roughly $35 for the starter set. For Kratky, the one-part powder is simpler and just as effective for leafy greens and herbs.
pH Testing and Adjustment
This is the one step that feels slightly technical, but it takes about 60 seconds once you get the hang of it. Plants absorb nutrients most efficiently when the solution pH sits between 5.5 and 6.5. Most tap water mixes with nutrients at a pH of 7.0 or above, so you will almost always need to bring it down.
A basic pH test kit with drops costs $8 to $10. A digital pH meter runs $15 to $20 and reads faster. General Hydroponics pH Down ($10 for an 8 oz bottle) is what most growers use to lower pH. A few drops per gallon usually does the job.
How to Set Up a Kratky System Step by Step
The whole process takes about 20 to 30 minutes. Here is what I do every time I start a new Kratky grow.
Step 1: Choose Your Container
Pick a food-safe, opaque container sized to your plant. Quart mason jars work for single herbs like basil or mint. 5-gallon buckets support larger plants like lettuce or peppers. If you are using a clear container, wrap it in tape or paint the exterior to block light.
Step 2: Prepare the Lid
Cut or drill a hole in the lid to hold the net cup. For mason jars, I trace the net cup rim onto the regular (non-ring) lid and cut with a utility knife. For bucket lids, a 3-inch hole saw makes a clean cut in seconds. The net cup should sit with its rim resting on the lid surface, not drop through.
Step 3: Mix the Nutrient Solution
Fill the container with water, leaving about an inch of space below where the net cup bottom will sit when the lid is on. Add nutrients according to the package directions. For MaxiGro, I use one level teaspoon per gallon and stir until the powder is fully dissolved. The water will turn a light greenish-yellow.
Step 4: Adjust the pH
Test the solution. It will almost certainly read above 6.5. Add pH Down a few drops at a time, stir, and test again. Getting into the 5.8 to 6.2 range is the sweet spot. This single step makes more difference to plant health than nutrient brand or container type.
Step 5: Place the Seedling in the Net Cup
Fill the net cup with clay pebbles. Nestle a seedling into the medium so roots poke through the bottom of the cup. The roots should just touch or barely dip into the nutrient solution. As the plant grows, roots extend deeper on their own. If starting from seed, germinate in a damp rockwool plug first (about a week), then transfer to the net cup once roots appear.
Step 6: Set It in a Well-Lit Spot
Lettuce and herbs need 12 to 16 hours of light per day. A south-facing windowsill works in summer. For consistent year-round results, a basic LED grow light on a timer fills the gap. I keep my Kratky jars under a simple clip-on grow lamp and run it on a 14-hour timer cycle.
Step 7: Monitor and Wait
Check the water level every few days. You will see it dropping as the plant drinks. That falling level creates the air gap that gives roots oxygen. Do not refill the container to the original line because you will drown the roots that have adapted to breathing in the air gap. Lettuce and most herbs reach harvest without needing a top-up at all.
Best Plants for Kratky Hydroponics
Not every plant suits this method. The best Kratky plants share a few traits: they grow relatively fast, they have modest water needs, and they reach harvest before a single fill of nutrient solution runs out.
| Plant | Container size | Days to harvest | Notes |
|---|---|---|---|
| Loose-leaf lettuce | Quart jar or bucket | 30-45 | Cut-and-come-again harvesting extends the grow |
| Basil | Quart jar | 21-30 | Fastest visible results, great for a first Kratky grow |
| Spinach | Quart jar or bucket | 35-45 | Prefers cooler temperatures, 60-70F |
| Mint | Quart jar | 28-35 | Grows aggressively, keep it in its own container |
| Cilantro | Quart jar | 30-40 | Bolts in warm conditions, so keep it below 75F |
| Kale | 5-gallon bucket | 50-65 | Needs a larger container and may need a nutrient top-up |
Herbs and leafy greens are the sweet spot. They are also the best plants for a hydroponic garden at any scale, which is why our hydroponic systems guide recommends starting with them regardless of which method you choose. If you want even faster harvests with almost no wait time, growing microgreens works well in a Kratky-style setup and produces edible greens in 7 to 14 days.
Fruiting plants like tomatoes and peppers push Kratky’s limits. They drink more water, need more nutrients, and take longer to mature. Cherry tomatoes can work in a 5-gallon bucket, but expect to top up nutrients at least once and possibly deal with root crowding. If you want to grow fruiting plants seriously, deep water culture handles them better because the air pump keeps roots oxygenated even as the plant’s water demand increases.
Common Problems and How to Fix Them
Root Rot
Brown, slimy roots usually mean the air gap disappeared. This happens when you refill the container too high and submerge roots that had adapted to air. The fix is simple: do not top up past the halfway mark once the air gap has formed. If roots are already rotting, trim the damaged sections with clean scissors and lower the water level so healthy roots sit above the surface.
Algae Growth
Green film on the container walls or nutrient surface means light is getting in. Wrap clear containers in tape, cover any gaps around the net cup with aluminum foil, and make sure the lid fits tightly. Algae will not kill your plants, but it competes for nutrients and looks unpleasant.
Nutrient Deficiency Signs
Yellowing leaves usually point to low nitrogen or pH that has drifted outside the 5.5 to 6.5 range. Check pH first. If pH is fine, the plant has likely used up most of the available nutrients and needs a partial refill with fresh solution. This is more common with longer-growing crops like kale or peppers than with lettuce or herbs.
Kratky vs DWC: When to Upgrade
Kratky and deep water culture start from the same idea (roots in nutrient solution), but they diverge in one important way: DWC adds an air pump and airstone to oxygenate the water constantly. That single difference changes what the system can do.
| Factor | Kratky | DWC |
|---|---|---|
| Electricity | None | Air pump runs 24/7 |
| Setup cost | $10-30 | $45-100 |
| Maintenance | Check every few days | Weekly pH and EC monitoring |
| Best plants | Leafy greens, herbs | Everything Kratky grows, plus tomatoes and peppers |
| Growth speed | Standard | Faster (constant oxygenation) |
| Failure risk | Very low | Pump failure can stress plants quickly |
Stick with Kratky if you are growing herbs and greens and value simplicity over speed. If you want something even simpler with zero setup, an AeroGarden automates everything but teaches you less about how hydroponics works. Move to DWC when you want to grow larger plants, get faster yields, or scale up to multiple buckets inside a grow tent. Ebb and flow hydroponics is another step beyond DWC for growers who want to run many plants through a single reservoir, but that is territory for after you have a few successful harvests under your belt.
Our DWC hydroponics guide walks through the setup process if you are ready for that next step.
What a Kratky Setup Actually Costs
One of the main reasons Kratky works so well for beginners is that the startup cost is genuinely low. Here is what I spent when I set up my first system and what it would cost if you bought everything new.
| Item | Mason jar setup | 5-gallon bucket setup |
|---|---|---|
| Container | $2-3 (quart jar) | $4-5 (bucket with lid) |
| Net cups (pack of 25) | $5-8 | $5-8 |
| Clay pebbles (2 lb bag) | $8-10 | $8-10 |
| MaxiGro 2.2 lb | $17 (lasts months) | $17 (lasts months) |
| pH test kit | $8-10 | $8-10 |
| pH Down 8 oz | $10 | $10 |
A single mason jar setup costs $12 to $18 if you already have jars. A bucket build runs $20 to $30. The nutrients, pH kit, and pH Down are shared across all your containers, so every additional plant only costs the price of a net cup, some clay pebbles, and a seedling.
Ongoing electricity cost is zero. The only recurring expense is nutrient powder, and a $17 bag of MaxiGro makes dozens of gallons of solution. This is the cheapest way to start growing food indoors, period.
Frequently Asked Questions
Does the Kratky Method Need an Air Pump?
No. The Kratky method is a passive system that uses no pump, no electricity, and no moving parts. As the plant drinks nutrient solution, an air gap forms naturally between the water surface and the container lid. That air gap provides the oxygen roots need. This is the main difference between Kratky and deep water culture, which uses an air pump to oxygenate the solution.
What Plants Grow Best With the Kratky Method?
Leafy greens and herbs are the best fit. Lettuce (especially loose-leaf and butterhead varieties), basil, mint, cilantro, spinach, and kale all perform well because they have modest root systems and reach harvest before the nutrient solution runs out. Peppers and small tomatoes can work in larger containers like 5-gallon buckets, but they need more attention and may require nutrient top-ups before harvest.
How Often Do You Add Nutrients to a Kratky System?
For lettuce and most herbs, you do not need to add nutrients at all. The initial fill lasts from planting to harvest (4 to 6 weeks). Larger or longer-growing plants like peppers may need a top-up after 3 to 4 weeks. When topping up, add fresh nutrient solution to about one-third of the original level so the air gap is preserved.
Is Kratky Better Than DWC?
Kratky is simpler and cheaper. It uses no electricity and requires almost no maintenance. DWC produces faster growth and supports larger plants because the air pump keeps roots constantly oxygenated. If you are growing leafy greens and herbs and want the easiest possible setup, Kratky is the better choice. If you want to grow tomatoes, peppers, or other larger crops, DWC is worth the extra cost and effort.
Can You Grow Tomatoes With the Kratky Method?
It is possible but not ideal. Tomatoes are heavy feeders that drink a lot of water and need consistent nutrient levels. In a Kratky setup, they can drain a 5-gallon bucket in a few weeks and may need multiple refills. Cherry tomatoes are more manageable than full-size varieties. For reliable tomato growing, a DWC system with continuous aeration is a better match.