Which hydroponic system for which plant? A Namibian grower's guide

You can grow almost anything hydroponically. That does not mean every system suits every plant, and this is where most first setups go wrong.

Put a tomato in an NFT channel and it will grow beautifully for six weeks, then its roots will block the channel and you will have nowhere to tie it up to. Put lettuce in a Dutch bucket and you have spent bucket money on a crop that would have been happy in a 100 mm channel. Neither failure is dramatic. You just quietly lose a season.

So work out what you want to grow before you buy anything. The plant chooses the system, not the other way round.

First, the big split: drain to waste or recirculating

Every hydroponic system falls into one of two camps, and the camp matters more than the brand name on the box.

Drain to waste (also called run to waste) feeds fresh nutrient solution to the plant, and whatever the plant does not use runs out the bottom and is not fed back in. Every drop the roots see is exactly the mix you made up. Nothing accumulates, nothing drifts.

Recirculating feeds the same body of solution round and round. It runs past the roots, drains back into a sump tank, gets pumped up again, and only leaves the system when you replace it. Far less water and fertiliser leaves the building, but the solution changes as the plants eat, so you have to watch it.

That third row is the one people miss. Fruiting crops move through a vegetative phase and then a generative phase, and they want a different feed in each. With drain to waste that is simple: the tank empties, you mix the next stage and carry on. On a recirculating loop everything drinks from the same tank, so in practice you run one schedule. Fine for lettuce, which is in one phase its whole short life. Limiting for tomatoes.

A word on the water-saving claim

There is an idea that hydroponics is always recirculating and therefore always extremely water efficient. It is water efficient, but there are levels to it.

From what I see in practice, a well-run drain to waste system uses roughly half the water of open-field drip irrigation for the same crop, and a recirculating system gets you to something like a fifth of it. Those are working figures from experience, not a lab result, so treat them as the shape of the thing rather than gospel. Set either next to flood irrigation or a pivot, still common here, and the gap stops being a debate.

So drain to waste is not the wasteful option. It is the one where you can measure the waste, and you should. Put a catchment under the slabs and the run-off tells you what the plant did not take: volume, EC and pH, compared against what you put in. That is the best feedback loop in hydroponics. Tighten the irrigation until you are draining a small, deliberate percentage rather than a puddle.

You cannot do that on a recirculating system. There is so much solution moving around that measuring the drain tells you nothing. You measure the sump instead.

Drain to waste systems, and what they are good for

Pulse irrigation into slabs

This is the workhorse of commercial fruiting-crop production, and it is not complicated. A dripper sits on top of a slab of growing medium and a timer gives short, frequent pulses of solution through the day.

The slab is usually one of two things. Rockwool slabs are the classic choice: fibre spun from molten rock, sterile, consistent and easy to steer with irrigation. Coco peat slabs or bags do a similar job with more buffering, and the coco coarseness can be matched to the crop, coarse for more air at the roots, finer where you want more hold.

Either way the plant sits in a cube on top of the slab, the drippers go in beside the stem, and the run-off drains away. That is still drain to waste even in the high-tech greenhouses that now capture, sterilise and re-use it: the capture is a water-recovery step bolted onto the end, not a recirculating root zone.

Best for: tomatoes, cucumbers, peppers, aubergines, anything long-running and trellised.

The other drain to waste setups

Slabs are the big one, but they are not the only one:

• Drip into pots or bags of coco, perlite or a coco and perlite mix. Exactly the same logic, in a container instead of a slab. This is how most small growers actually start, and it works.
• Hand-watered coco. No pump, no timer, you pour the solution in the top until a little runs out the bottom. Unglamorous and completely valid for a handful of plants.
• Sand or gravel culture. Older, still used in dry regions with cheap local media. Heavy, and hard to steer precisely.

You will also see ebb and flow (flood and drain) tables described as drain to waste. They usually are not: the classic version floods the tray from a tank and drains straight back into it, which makes it recirculating. Only if you dump the tank after each flood does it become drain to waste, and few people do.

Recirculating systems

Deep water culture

Deep water culture is the best known recirculating system and the principle is as simple as it gets: the roots hang in the nutrient solution the whole time.

In a commercial layout it is a shallow pool with floating rafts on top. Those rafts are polystyrene, the expanded stuff you know as Styrofoam or Styropor. Each raft has holes, each hole holds a net cup, and the plants sit in the cups with their roots fully submerged.

Two things follow from "fully submerged".

The first is oxygen. Roots need it, and a big still body of water does not have much. Deep water culture is not optional about aeration: you need an air pump and air stones running all the time. No air, no roots.

The second is a real advantage here. A large mass of water changes temperature slowly. Inland Namibia gives you hot days and cool nights, and a small reservoir rides that swing all the way up and all the way down. A deep water culture pool buffers it, and that thermal mass is one of the best arguments for the system in Windhoek.

The layout also scales beautifully. Push new seedlings in at one end and the rafts shuffle along, so you end up with a propagation side, a harvest side, and a steady conveyor between them.

Which is also why fruiting crops do not fit. The rafts move, so anything you trellis to would have to move with them, and a tomato will grow a root mass that fills the pool and makes proper aeration a fight. Cauliflower and spinach might be worth an experiment. I have not seen anyone here try it, and hydroponics rewards people who do.

Best for: lettuce, leafy greens, herbs, and soft berries like strawberries.

At home you do not need a pool. A 25 L bucket kit is the same physics in one container, and the cheapest honest way to find out whether you like the system.

NFT, nutrient film technique

This one is close to my heart. I have an NFT system at home that has been running continuously for about three years. These systems are close to unbreakable.

A pump lifts solution from the sump into a distribution manifold, which splits it into small feed lines, one per channel. Each channel sits on a slope, so a thin film runs down its length and back into the sump. The plants sit in net cups along the top with their roots trailing in that film. (Our NFT setup guide walks through the build itself.)

The key detail is in the word "film". The roots are only partly submerged, so they take oxygen from the air in the channel and from the moving water. That means no air pump needed, one less thing to buy and one less thing to fail.

On flow rate, do not overthink it. A lot gets written about the exact litres per hour a channel should carry. Make sure water is running and moving. I have had half-blocked feed lines dripping barely anything into a channel and still pulled a good crop off it. That is not a recommendation to run your system half-blocked, it is a reason not to lie awake about flow rates.

The sump tank is also your control room, where your pH and EC meters live, either dipped in when you check or hung in permanently.

The big advantage over deep water culture is response time. If your pH has drifted, you adjust the sump and the correction reaches the plants on the next pass. Same with nutrients. Deep water culture has a sump too, but it has that large pool as well, and anything you add takes a long time to work through. The thermal mass that helps with temperature works against you when you need to change something in a hurry.

Heat, and what the science actually says

The usual objection is that NFT cannot handle Namibian heat because there is so little water in the channel. Fair, so let us be precise.

For deep water culture the target root-zone range is roughly 18 to 22 °C, with problems appearing above about 25 °C, for two reasons. Warm water holds less oxygen: fully saturated fresh water carries about 9 mg per litre at 20 °C but only about 7.5 mg per litre at 30 °C, and Windhoek's altitude takes a little more off the top. At the same time Pythium aphanidermatum, the root rot organism, does its worst work at roughly 23 to 27 °C. Less oxygen and a happier pathogen, at the same moment. Media-based systems are more forgiving, closer to 20 to 25 °C.

Now the real-world part. My own system in Windhoek regularly runs at 30 °C and higher, well outside all of that, and the plants still grow. They take up minerals less efficiently than they would at 20 °C and I would not run a commercial operation that way, but "warmer than ideal" is not the same as "will not work". Beginners get scared off by a number rather than by a result.

There are cheap ways to take the edge off:

• Sink the tank into the ground. Soil at depth is far more stable than air.
• Use a bigger tank. Even a small home system should have at least 100 L. Volume alone buys you a lot of temperature stability.
• Keep the tank out of direct sun, and shade or insulate the channels if you can.

Round channels are a trap

Plenty of people start with round pipe, and I did too. It is cheap, available, and it will get you growing.

What I found over time is that round channels are impractical to live with. They roll. You will be shifting them about, you will want them on a bench, and they will not stay put. It gets worse the heavier the crop, and lettuce is heavier than you think. I once grew lettuce in round channels that got so big the plants toppled over on the system itself, at mounting points that were supposed to hold them. A mess by harvest.

That is why the only channels we sell are the rectangular ones. Our Marley food-grade NFT channels are a 100 x 50 mm profile, sold per metre at N$109 up to 6 m lengths, with moulded stop ends. Food grade and UV stabilised matters twice over here: the sun destroys ordinary PVC, and you do not want microplastics shedding into water your food grows in.

Six metres is available, but I would not go past 3 m in practice. A 2 m channel is a good starting point, and the system scales by adding channels rather than lengthening them. Pair them with 50 ml net cups, 55 mm across the top, which drop straight in.

If you would rather not build it yourself, our NFT Hydroponic Starter Kit, the Windhoek 20, uses these same channels and comes ready to run from N$2,990.

Best for: lettuce, herbs, leafy greens, short-cycle crops. You can grow almost anything in NFT, but fruiting crops will block the channels with root mass, and an NFT bench sits at table height, which makes trellising awkward and reaching the back channels worse.

Dutch buckets

Dutch buckets are where a recirculating system finally works properly with fruiting crops, and they are excellent.

Each plant gets its own bucket, typically 15 to 20 L, filled with an inert medium. A feed line drips into the top and an outlet in the base drains the excess into a return line back to the sump. Same recirculating principle as NFT, entirely different shape.

That shape is the whole point. The bucket is a heavy, stable base that will not tip. It sits low, so the plant has the full height of your greenhouse to climb into. It never moves, so you can put a permanent trellis above it and leave it there for the season. Everything a tomato wants.

Point the outlet down. Roots do not grow upwards, so a downward-facing elbow or siphon in the base stays clear where an upward-facing one blocks. Simple rule of nature, and it saves a lot of unpleasant work.

On medium: perlite is the standard, sometimes mixed with coco peat. There is already plenty of moisture moving through a Dutch bucket, so you do not need a medium that holds much more. Straight perlite usually does it.

People do use leca, and there is a catch. Round leca pebbles are so coarse that water runs straight down the middle of the bucket instead of spreading out, and roots at the outer edge can end up hanging dry. Perlite is fine enough to wick the solution sideways through the whole bucket. If you want leca's advantage, that it is reusable where perlite really is not, use crushed leca. We stock the 4 to 10 mm crushed grade, fragmented rather than round, and it distributes moisture properly.

Plumbing is the same as NFT: pump, distribution line, small feed lines into each bucket, return to the sump, meters in the sump. Run it on a timer or continuously, and it does not need much flow, a half-open 4 mm line per bucket is plenty.

Best for: tomatoes, peppers, cucumbers, and other long-running fruiting crops. We are planning to stock Dutch buckets, so watch this space.

The one that fits in neither camp: AutoPot

AutoPot is not drain to waste and it is not recirculating, and I love it.

A reservoir stands higher than the plants, gravity feeds solution down to a tray under each pot, and a valve in the tray controls the whole thing. No pump, no power. For anyone growing on a plot without mains electricity, that is not a convenience, it is the difference between growing and not growing.

The valve is the clever bit. It is not an ordinary float valve topping the tray up continuously. The AquaValve fills the tray, then shuts and stays shut until the tray is completely empty, and only then refills. So the pot goes through a full wet cycle followed by a full dry-out, over and over.

That dry phase is the magic. The roots at the base of the pot get to breathe on every cycle, which is what suppresses the fungal problems that come with roots sitting permanently wet. The system gets its own root health right, with no pump, no air stone and no input from you.

Fill the pots with a perlite and coco peat mix. A 50:50 blend is the standard starting point, and some growers go 70:30 in favour of perlite for more air. Both are worth trying, because trying things is most of hydroponics.

Then top up the reservoir with solution at the right pH and EC, and leave it. That is the whole job. The most hands-off hydroponic system I know, it handles fruiting crops well, and I have had excellent results with it myself.

We are AutoPot stockists here in Namibia, so spares are local and you can ask us before you buy, because we actually run these systems. Kits start at N$1,870 for the Easy2Grow, and the full range is on the AutoPot collection page. Some kits come with a reservoir and some without, so if you already own a suitable tank you can buy the system on its own and plumb it in.

One more thing worth knowing: the Tray2Grow planter box opens the door to root crops, which most hydroponic systems will not take. Ginger and garlic in coco peat go absolutely mad in a setup like that. Potatoes too. If you have written off root vegetables as impossible without soil, try one box.

What about the other systems?

The four above are the ones I would put money on in Namibia. For completeness, here is the rest of the field and what I make of it.

Choosing yours

The one thing to take away

Match the system to the shape and the length of the crop, not to what looks clever in a photograph. Short-cycle leafy crops want water and volume, and NFT or deep water culture gives them that cheaply. Long-running fruiting crops want a heavy base and something to climb, and that is Dutch buckets, AutoPot or slabs. Get that one decision right and everything after it, the pump, the medium, the feed, gets easier.

And once it is running, try something outside the list. Nobody knows yet what grows best in Namibian conditions, because not enough people here have tried it. Hydroponics is a trade you learn by testing.

Not sure what to feed it once it is built? Our free nutrient calculator works out the mix for your crop and your system, and the Hydroponics Bootcamp walks you through the whole thing in person.

Frequently asked questions

What is the difference between a drain to waste and a recirculating hydroponic system?
In a drain to waste system, the nutrient solution passes the roots once and the run-off is discarded, so every feed is fresh and exactly the mix you made. In a recirculating system the solution drains back into a sump tank and is pumped round again, which uses less water and fertiliser but means the mix drifts as plants feed and needs monitoring.

Which hydroponic system is best for tomatoes?
Dutch buckets, AutoPot, or drip irrigation into rockwool or coco slabs. Tomatoes run for months, get heavy and need trellising, so they need a stable base that stays in one place. Avoid NFT and deep water culture: the root mass blocks channels and fills pools, and neither gives you anywhere sensible to tie the plant.

Do I need an air pump for an NFT system?
No. NFT runs a thin film of solution so the roots are only partly submerged and pick up oxygen from the air in the channel and from the moving water. Deep water culture is the opposite: the roots are fully submerged, so an air pump and air stone are essential.

What water temperature should a hydroponic system run at?
Aim for about 18 to 22 °C in deep water culture, and roughly 20 to 25 °C in media-based systems. Above about 25 °C the water holds less oxygen and root rot organisms such as Pythium become more active. In Namibian heat you can still get a crop above that, but you lose efficiency, so sink the tank, run at least 100 L and keep it out of the sun.

Can I grow root vegetables hydroponically?
Yes, in a system with enough depth of medium. An AutoPot Tray2Grow style planter box filled with coco peat handles ginger, garlic and potatoes well. Channel and raft systems will not, as there is nowhere for the crop to form.

Further reading

• Best Hydroponic Kits for Beginners: 2026 Buyer's Guide
• NFT hydroponic systems: setup guide for first-time growers
• Deep Water Culture Buckets: How to Set Up and What to Buy
• Lime in your borehole water? Managing hard water in Namibian hydroponics