Getting started with hydroponics: which system to build first

Kratky, DWC, drip, and NFT compared for cost, complexity, and crop range. What to build if you've never grown without soil.

Hydroponics has a marketing problem. Search for "how to start hydroponics" and you get expensive commercial setups, YouTube builds with custom-welded frames, and ad-supported listicles ranking ten systems you don't need. The actual entry point is a mason jar, some nutrient solution, and a lettuce seedling.

This covers the four common system types, what each one is good and bad at, and which one to build first depending on what you want to grow.

The four systems

Kratky (passive, no pump, no electricity)

A container of nutrient solution with a net pot sitting in a hole in the lid. The plant roots grow down into the solution. As the plant drinks, the water level drops, leaving an air gap between the lid and the water surface. Roots in the air gap absorb oxygen; roots below the water line absorb nutrients. The system self-regulates.

Cost: minimal. A 5-gallon bucket, a net pot, some clay pebbles, and nutrient solution.

Power: None. No pump, no air stone, no timer. The system runs on gravity and evaporation.

Good for: Lettuce, herbs (basil, cilantro, mint), leafy greens, peppers in larger containers. Any crop that finishes before the reservoir runs dry.

Bad at: Tomatoes and cucumbers. Heavy fruiting crops drink the reservoir faster than the air gap can form, and the roots don't get enough oxygen. It works in theory but the yields are poor compared to an active system.

Why start here: Zero failure modes from equipment. No pump to fail, no timer to mis-set, no air stone to clog. If the plant dies, it's a nutrient or light problem, not a plumbing problem. That narrows the debugging to two variables instead of ten.

DWC (deep water culture)

A reservoir of nutrient solution with an air pump and air stone bubbling oxygen into the water. Net pots sit in holes in the lid, roots submerged full-time. The air pump provides the oxygen that Kratky gets from the air gap.

Cost: moderate. Same bucket as Kratky plus an aquarium air pump, air stone, and tubing.

Power: Air pump runs 24/7. Draws 3-5 watts; negligible on the electricity bill.

Good for: Everything Kratky does, plus larger fruiting crops. Tomatoes, cucumbers, and peppers grow well in DWC because the continuous aeration supports the root oxygen demand that Kratky can't sustain. The reservoir is larger (typically 15-20 gallons for tomatoes), and the air stone keeps the solution well-oxygenated even in warm water.

Bad at: Root crops (carrots, beets, radishes). The roots hang in water; there's no solid medium to shape them. Also bad if the power goes out; without the air pump, roots drown within a few hours in warm nutrient solution. A cheap battery backup for the air pump is worth having.

Drip (top-feed with media)

A pump on a timer pushes nutrient solution from a reservoir to drip emitters at the top of each plant container. The solution drips through a growing medium (perlite, coco coir, or clay pebbles), past the roots, and drains back to the reservoir. Sometimes called "Dutch bucket" when using individual 5-gallon containers.

Cost: variable depending on the number of plant sites. Reservoir, submersible pump, timer, tubing, drip emitters, growing media, and containers.

Power: Pump runs on a timer, typically 15 minutes on, 45 minutes off, cycling several times per day. Draws 5-20 watts depending on the pump size.

Good for: Heavy fruiting crops. Dutch bucket drip systems are the commercial standard for hydroponic tomatoes, peppers, cucumbers, and eggplant. The media provides physical root support for heavy plants, and the intermittent flooding gives roots alternating access to nutrients and oxygen.

Bad at: Lettuce and herbs. They grow fine in drip, but the system is overbuilt for small crops. A Kratky jar does the same job for a tenth of the cost.

NFT (nutrient film technique)

A thin film of nutrient solution flows continuously through angled PVC pipes or channels. Net pots sit in holes in the top. Roots grow into the film. The solution returns to a reservoir and recirculates.

Cost: higher. Reservoir, pump (runs 24/7), PVC pipes or channels, net pots, end caps, and a return manifold.

Power: Pump runs continuously. Draws 10-30 watts.

Good for: Lettuce, herbs, and leafy greens at scale. NFT is space-efficient, water-efficient, and looks clean. Commercial lettuce operations use NFT or DWC almost exclusively.

Bad at: Anything heavy. A mature tomato plant's root mass clogs the thin channel. Fruiting crops need more root zone volume than NFT provides. Also fragile: if the pump fails, the thin film dries out in under 20 minutes and roots start dying. No buffer.

Which one to build first

If you've never grown without soil: Kratky. Grow a head of lettuce in a mason jar on a windowsill. Total investment is a few dollars and 30 minutes. If the lettuce grows, you understand the basics of nutrient solution, pH, and plant nutrition. Scale up from there.

If you want to grow tomatoes or peppers: Skip Kratky and go to DWC (single bucket for one or two plants) or drip (Dutch buckets for more). Both handle the fruiting-crop oxygen demand that Kratky can't.

If you want a wall of lettuce: DWC raft or NFT. Both scale horizontally. NFT is more compact; DWC is more forgiving.

Nutrients

All hydroponic systems need a nutrient solution. The plant gets everything from the water; there's no soil to provide minerals.

Two-part or three-part liquid concentrates (General Hydroponics Flora series, Masterblend, Jack's Hydro) are the standard for home growers. You mix Part A and Part B (and sometimes Part C) into water at a specified ratio per gallon. Two-part systems keep calcium separate from sulfates and phosphates because they precipitate if stored together in concentrate.

EC and pH are the two numbers you monitor. EC (electrical conductivity) measures the total dissolved nutrient strength. pH determines which nutrients the roots can absorb. Most crops want EC 1.0-2.5 mS/cm and pH 5.5-6.5. The EC/PPM converter handles the unit conversion between EC and the common ppm scales. The nutrient mixing calculator computes target ratios by crop and growth stage.

Tap water is usually fine as the base. Municipal water with an EC below 0.5 mS/cm and pH 6.5-7.5 works for most crops without pre-treatment. Hard well water (EC above 0.8, or GH above 15) may need dilution with RO water. Very soft water (GH below 3) may need supplemental calcium and magnesium.

pH adjustment: Most tap water starts above 7.0; nutrient solution needs to be 5.5-6.5. pH-down solution (phosphoric acid) is the standard. A few ml per gallon, added after mixing nutrients. Check with a pH meter or drops, not paper strips.

Common first-timer mistakes

Too much light, too little nutrient. Indoor growers buy a powerful LED panel and wonder why growth stalls. The plant can only use light in proportion to the nutrients available. Match light intensity to EC; the grow light calculator helps size the light to the crop.

Not checking pH after mixing nutrients. Nutrients lower the pH of tap water, but usually not enough. The final solution pH should be 5.5-6.5. Outside that range, some nutrients lock out and the plant shows deficiency symptoms even though the EC is correct. Iron lockout above pH 6.5 is the classic example: the nutrient is in the water but the roots can't absorb it.

Refilling the reservoir with fresh nutrient solution instead of plain water. As plants drink, water leaves the reservoir faster than nutrients. The EC creeps up. Topping off with more nutrient solution concentrates it further. Top off with plain pH-adjusted water; only add fresh nutrients when the EC drops below target.

Starting with tomatoes. Tomatoes are the crop everyone wants to grow first and the worst choice for a beginner. They need high light (DLI 22-30), high EC (2.5-3.5 in fruiting stage), support structures, pruning, pollination (no bees indoors), and 4-5 months to first fruit. Start with lettuce. It produces a harvest in 30-45 days, tolerates low light, and forgives every mistake you'll make with nutrients and pH.

Your first week: a Kratky lettuce walkthrough

If you've never grown hydroponically, start here. This is the minimum viable hydroponic setup: one plant, no pump, no timer, results in 30 days.

Day 1 (setup, 15 minutes): Get a wide-mouth quart mason jar ($3), a 3-inch net pot ($1 for a pack of 10), a handful of expanded clay pebbles or perlite ($5 for a bag that lasts years), and hydroponic nutrient (General Hydroponics MaxiGro, $12 for a bag that lasts months). Fill the jar with tap water, add about half a teaspoon of MaxiGro per litre, stir until dissolved. Test pH with a cheap pH pen ($10-15); adjust to 5.8-6.2 with a drop of pH-down solution. Place the net pot in the jar's mouth. Fill it with clay pebbles.

Day 1 (planting): Tuck a lettuce seedling (started in a rockwool cube, peat pellet, or borrowed from a garden center) into the net pot so the roots dangle through into the nutrient solution. If starting from seed, place 2-3 lettuce seeds on a moist piece of paper towel in the net pot, cover lightly with pebbles, and keep the surface moist until germination (3-5 days).

Day 2-7 (observation): Place the jar on a bright windowsill or under a small LED light (even a desk lamp with a daylight bulb provides enough light for a single lettuce). Roots begin extending into the solution. The plant grows slowly as it establishes.

Day 7-14: Visible growth. Roots are now several centimeters long and may be visible through the jar. The water level has dropped slightly from the plant's uptake. Don't top up yet; the air gap forming between the water surface and the net pot is important. It allows air roots to develop, which provide oxygen to the root system.

Day 14-21: The lettuce grows noticeably faster as the root system matures. Top up with plain pH-adjusted water (not more nutrient solution) when the water level drops to half the jar's volume. Leave the air gap intact.

Day 25-35: Harvest outer leaves as needed, or cut the entire head when it reaches the size you want. Start a second jar a week before harvesting the first so you have continuous lettuce.

Total cost: Under $30 for everything including the pH pen. The nutrients and pebbles last for dozens of grows. The ongoing cost per head of lettuce is pennies.

This single-jar experience teaches you pH management, nutrient mixing, and root zone observation. Every hydroponic system, no matter how large or complex, uses these same principles. Once you've grown three or four successful heads of lettuce, you understand the fundamentals well enough to build a multi-plant DWC, NFT, or drip system and know what you're looking at when something goes wrong.

Scaling from one jar to a real system

The Kratky jar works for 1-5 plants. Beyond that, the number of individual containers to manage becomes impractical. The next step is a shared-reservoir system where multiple plants draw from a single nutrient solution.

DWC bin (5-15 plants): A 40-80 liter plastic storage bin with a lid, holes cut for net pots, and an air stone connected to a small aquarium air pump. Fill with nutrient solution, aerate continuously, and the plants grow faster than Kratky because the air stone provides consistent dissolved oxygen to the root zone. Cost: $30-50 for the bin, air pump, and air stone. This is the most popular home hydroponic system for a reason.

NFT channel (15-30+ plants): Vinyl rain gutters or purpose-built NFT channels mounted on a slight slope, fed by a small pump from a reservoir. Water flows in a thin film along the bottom of the channel, past the net pot roots, and drains back to the reservoir. Excellent for lettuce and herbs because the plants sit in the channel at uniform spacing and the system can be mounted on a shelf or wall. Cost: $60-150 for a basic 2-channel system with pump and reservoir.

Drip system with Dutch buckets (4-20 plants): Individual buckets (one per plant) fed by drip emitters from a central reservoir. The nutrient solution drips into the top of each bucket, flows through the growing media (perlite or a perlite/vermiculite mix), and drains back to the reservoir. Best for large plants (tomatoes, peppers, cucumbers) that need individual root zone volume. Cost: $80-200 depending on the number of buckets.

Each of these systems builds on the same principles you learned with the Kratky jar: nutrient concentration (EC), pH management, and root zone oxygenation. The complexity increases, but the core knowledge transfers directly.

The EC to PPM converter and nutrient mixing calculator support you as you scale up.