Choosing Your Cultivation System
By Hydro Harvest
- 22 May 2025
Once you know the basic differences between Active and Passive Cultivation Systems there’s a fair chance, you’ll have an idea of which way you want to go. Often a grower’s personal ‘ideals’ about how a plant should grow will be decisive.
But there are still factors aplenty to consider. Look below before putting your money down. Running through the functions, benefits, and drawbacks of each system type might lead you to surprise yourself.
Control
Timers, pumps, and even basic computers manage the watering and feeding with an Active cultivation system. Because you can set these devices to dictate the feeding regime you have a whole lot more control with this kind of setup than with Passive.
Plant capacity
Both Active and Passive systems will take up a larger footprint than hand-watered pots on a tray. That means you’ll potentially be looking at fewer plants. But you’ll likely be looking a much bigger plant too. The yield from system-grown plants can easily outweigh their reduced numbers. So, you’re not actually losing out. Far from it.
The second thing to say about plant capacity is that certain different, specific products give you space and/or flexibility. Active systems like R-DWC, Wilma, and Flood and Drain can require pipework and hardware that isn’t all that flexible in terms of positioning. Add to this, they suspend your plants in an elevated position which slightly reduces headroom.
Passive systems such as AutoPot involve pipework and fittings – just like the Active systems named above. But the routing of such kit is more flexible and the pot and tray ‘modules’ in which the plants grow tend to be much more space efficient.
Choice of nutrients
Passive cultivation systems give you the best of both worlds in that you can run mineral and/or organic feeds and embrace bioactivity. With Active systems you are pretty much looking at mineral-based feeds only. That’s largely down to the environment within an Active system, the substances you need to use to maintain them, and the type of grow media you’ll need to use.
Choice of grow media
In an Active cultivation system, a small amount of natural grow media might be involved. You can use coco in certain types of Flood and Drain system. But, likely as not, with an Active system your plants will be rooted in clay pebbles or rockwool.
Whilst rockwool will wick some water and nutrient solution to the roots, such materials mainly act as a means of supporting plants. Pebbles and rockwool allow the roots to hang in close contact with water and nutrient solution for maximum exposure to growth stimulating aerated irrigation and feed.
As Passive systems typically employ traditional, plastic or fabric pots you can use them to get the very best out of a vast range of natural grow media. Soil, coco, and any number of improvised materials can be combined with supplementary ingredients such as perlite, vermiculite, rockwool, and pebbles to create a rich, bio-friendly, aerated home for your roots. Better still, your plant roots will be somewhat insulated against shocks of temperature or fluctuating levels in your water and nutrient solution.
Maintenance
Topping up the reservoir, monitoring levels, refreshing nutrient solution – all this can be done in a single, weekly or twice weekly visit. In theory there’s no real difference in the number of visits required for Active or Passive systems, although attention to levels with an Active system might make you want to pay an extra call or two.
Beyond that you might want to think about how much effort you want to put into monthly, post-harvest, and yearly servicing. All systems will ultimately need cleaning. If cost and effort matter on that front, then Passive systems are probably marginally easier and cheaper but not by much.
Tuning
With great power comes great responsibility. So, it goes with Active systems. You can achieve amazing results thanks to their tech-driven, easily directed features. But you need a little bit more understanding of how to tune the systems than with Passive.
For example, with an Active system such as Flood and Drain you need to carefully set up the frequency, depth, and duration of the flood period. Frequency alone is determined by the grow media you’re using, the size of your plants, the environment in your room, and plant uptake.
DWC systems such as OxyPot are a simpler Active option. But you do have to keep a very close eye on water temperature, water levels, nutrient concentration, and pH.
Passive systems such as AutoPot which run based on plant consumption require no real system calibration. Plants simply draw what they need when they need it. The results can be less dramatic than those achieved with Active systems. But with a little of your extra spare time redirected to the plants themselves you can get some very nice harvests indeed.
Modularity
Some Active systems such as Wilma or NFT combine multiple pots or plant sites with a built-in reservoir. Because of their compactness, simplicity, and all-in-one arrangement these can appeal to some growers. But they’re not as flexible as ‘modular’ systems.
In a modular system each plant goes in a separate pot that goes in its own tray or bucket. That’s your module. Each module is connected via pipework to a wider system. The system is served by a separate reservoir.
Examples of Active modular systems include R-DWC and Flood and Drain whilst the prime Passive example is AutoPot. These can be arranged quite flexibly, and you don’t have to have your reservoir in your tent – which helps you control water and nutrient temperature.
Better still, with a modular system you can add extra modules easily, making expansion an inexpensive affair. Passive systems such as AutoPot make this even more straightforward with truly ‘standalone’ modules. As there’s no power, running water, or waste plumbing involved you can get in, make changes, and get out quickly.
OxyPot systems give you the best of both worlds in terms of self-contained growing and modular flexibility. These Active systems look like the modules of a wider system. But the reservoir is built into the unit beneath the plant site – with no external reservoir or pipework required. And that brings us nicely onto system requirements.
System requirements
As we’ve mentioned, Active cultivation systems promote phenomenal growth and produce yields that are very difficult to rival with other techniques. To do this they require pumps, power, and waste drainage.
These requirements mean that Active systems are more easily noticed than Passive systems. A lot of Passive systems produce little or no waste, use no electricity, and run silently. If discretion and low overheads are a priority you might want to bear this trade-off in mind.
Recirculation
To maintain the constant, intensive flow of water and nutrient solution some Active systems employ recirculation. R-DWC, Flood and Drain, NFT, and Wilma – we’re looking at you.
At it’s simplest, a recirculating system is any system where the same water and nutrient solution passes between all the plants, goes back to the reservoir, and then repeats it’s journey.
The upside is just how regularly your plant roots are exposed to aerated, nutrient rich water. And it’s more efficient than a Run-To-Waste system where unused water and nutrient solution is drained off. If the water and nutrient solution are properly monitored and well-kept, recirculating systems can be spectacularly effective. But they do require close attention.
If you don’t maintain the water and nutrient solution and stay on top of plant health, then problems can spread rapidly around the system. In some cases, you’ll just be supplying a depleted feed to all your plants. Worst case scenario would be dangerously imbalanced levels in your solution or the spread of root problems between plants.
To keep on top of your levels you’ll probably want to change out your entire water and nutrient solution every week or so. That means a little extra work in terms of shutdown time and labour. It also means disposing of waste fluids – so you’ll need a drain handy.
OxyPot gets around the issue of sharing feeds by having DWC modules that each include their own built-in reservoir. The plants get all the benefits of an Active system whilst remaining totally isolated.
Passive cultivation systems such as AutoPot don’t involve recirculation either. Nothing passes between the individual modules. You will still need to monitor levels and refresh your reservoir but the need to do so is less critical, plus waste is far less of an issue.
The bottom line
You can look at it a couple of ways. Yes, all cultivation systems involve a trade-off. But on the other hand, these same trade-offs are part and parcel of the differences that mean there is something for every type of grower.
If you’re into high performance, accelerated growth, and boundary-pushing yield you’ll likely be fine with making the arrangements necessary for an Active cultivation system.
If you prefer more natural, characterful plants grown in bioactive media with minimum fuss then you’ll probably take the marginal drop in pace and yield associated with a Passive system.
The good news is that these systems are all proven, established, successful means of cultivating healthy, fruitful plants. Because they are ‘industry standards’ there’s a whole world of supporting products and growers’ knowledge out there to back you up. As soon as you know the way you want to grow it’s easy to get out there find what you need, find your ‘tribe’, and make it happen.