Getting started with hydroponics: which system to build first

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 dissolved oxygen above 6 mg/L 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, PPM-500, and PPM-700 scales. The nutrient mix 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 20-30), 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.