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How to Build a Hydroponic Wick System

By: Chris | Last Updated: December 29, 2021

I love root vegetables. There’s just one problem. Most hydroponic systems aren’t very well suited to growing root vegetables.

My first attempt at growing a hydroponic radish was done in an ebb and flow system. That didn’t work out very well. The clay pebbles were too restrictive and caused the radish to shoot up out of the media as it grew. Not the most ideal situation.

In a hydroponic setting, vegetables like radishes and carrots need a media bed that’s deep enough to support downward and outward root growth. In order to give these plants plenty of room to grow, I decided to build a basic wick hydroponic system.

This is a good hydroponic system for beginners. It can be made as a completely passive system, meaning there are no moving or electrical parts. This means less cost to build, and a more affordable way to give hydroponic gardening a try.

How Does Wick System Hydroponics Work?

Wick system hydroponics works by using absorptive fabric to pull water from a reservoir up into a media bed via capillary action.

Roots also use capillary action to transport water up into the growing plant. This is the same phenomenon you can experience by dipping the end of a paper town in a glass of water and watching the water “crawl” up the paper towel.

The fabric wicks act like flexible plumbing pipes running water from the bottom tote up to the growing area in the top tote. Several drain holes are drilled into the top tote so that excess water can drain back down into the reservoir.

This helps reduce the chances of nasty things like mold and mildew.

Once in the growing area, some of the water is absorbed by the growing medium and some is absorbed directly by the plant roots.

Air stones in the reservoir are not required, but they help oxygenate the water and keep it from becoming stagnant.

Growing Media for Wicking Systems

The media in a hydroponic wick system is important as well. We want something that will hold some moisture without becoming waterlogged and want something that will allow root vegetables to easily expand as they grow.

Expanded clay pebbles (LECA, hydroton, etc) are excellent at holding moisture without becoming oversaturated. One problem though, root vegetables have a hard time expanding in this hard grow medium.

Coco coir holds moisture and is soft/pliable enough to allow root veggies to expand, but there’s still a problem. Coco by itself retains way too much moisture and will likely lead to root rot.

Preferred Media for Wick System Hydroponics

The best media mix I’ve found for wicking beds is a mixture of 60% perlite and 40% vermiculite. Both media are relatively loose and allow for the rapid growth of root vegetables.

Hydroponic Wick Grow Medium

Perlite holds less moisture than vermiculite and helps prevent the media from holding too much water. The vermiculite’s job is to hold water to be absorbed by the plant’s roots.

Wick System Supplies

Wick systems are inherently simple and only need a few supplies.

Coarse perlite is a great choice to pair with vermiculite. I recommend buying both perlite and vermiculite at a local garden center or farming co-op. The prices will be a lot more affordable.

Recommended Tools

Recommended Additional Supplies

If you want to make a completely passive system (no electrical/moving parts), you can skip out on getting the aerator, air stone, and grommets.

You’ll have a totally off-grid hydroponic system, but you’ll need to keep an eye on the nutrient solution as it will become stagnant over time as dissolved oxygen is absorbed by the plants.

How to Build a Wicking Hydroponic System

Building this hydroponic wick system is pretty straightforward. As long as you can operate scissors, a drill, and a box cutter, you’re qualified to make this happen.

Step 1 – Cut Wicking Cord

Cut 6 to 8 sections of wicking cord. Each section should be 15 to 20 inches long. This should be long enough for the cord to extend from the bottom of the reservoir to the top of the growing area.

Step 2 – Drill Holes for Wicking Cord

Drill Holes for Wicks

On the bottom of the growing area tote (top tote), drill one hole for each wicking cord you cut. The hole size should be around ¼” diameter if you’re using ¼” cord. Don’t make the hole oversized. The cord should fit snugly around the hole. Space the holes out to provide moisture to the entire growing area.

Step 3 – Drill Drain Holes

Using a ⅛” drill bit, drill several drain holes around the bottom of the growing area tote. This will allow excess moisture to drain back down into the reservoir.

Step 4 – Run Wicking Cord

Run the wicking cords through each of the wicking holes you drilled earlier. Make sure the cords hang down far enough to touch the bottom of the reservoir tote (bottom tote).

Step 5 – Cut the Lid

Cut the Reservoir Lid

The lids that come with the totes can be cut to keep the top tote from sliding all the way down into the bottom tote. To do this, simply cut out the inner section of the lid.

If you use a box cutter, make several shallow cuts.

Step 6 – Secure the Wicks

Secure Wicks with Reservoir Lid

Drape the wicks over the lip of the top bucket, and then put the cutout lid on to hold the wicks in place while you fill the bucket with media. This keeps the wicks from falling down and getting covered up.

Step 7 – Add Expanded Clay as a Filter

Add expanded clay pebbles or small river rocks to the bottom of the growing area tote. This will act as a filter to keep perlite and vermiculite from draining down into the reservoir.

Expanded clay and river rocks have a lot of dust on them, so rinse them really well before adding them to the tote.

Step 8 – Mix Perlite & Vermiculite

Make a 60/40 mix of perlite and vermiculite. That’s 60% perlite to 40% vermiculite.

Perlite and vermiculite contain a ton of dust, make sure to rinse the mix thoroughly with water before using. I rinse the mix in a cheap fabric pot so it will drain quickly.

Note: It’s not healthy to breathe perlite or vermiculite dust. Wear a dust mask, and mix them outdoors.

Step 9 – Add Media Mix to Top Tote

Start adding the perlite/vermiculite mix to the top tote. As you do this, move the wicks to keep them in position, otherwise, the media will push them to the sidewalls of the tote.

Fill the tote to within 3 to 4 inches of the top lip, then take the lid off the tote, and lay the wicks over as shown in the picture. This will keep the wicks 3 to 4 inches from the surface.

Pull any excess wicking material down through the bottom of the tote. This will provide extra wicking material inside the reservoir.

Lay the Wicks Over

Once the wicks are in position, add media to within 1 inch of the top lip.

Step 10 – Install Aerator & Air Lines (Optional)

If you’re using an aerator, drill one hole on each side of the bottom tote about 2 inches below the handhold. If you’re using the top hat grommets, use a 25/64 drill bit. If you’re not using a grommet, use a 3/16 drill bit.

When you cut the airlines, try to keep them both the same length. This helps make sure each line gets the same amount of pressure.

Step 11 – Add Water, Nutrients, & Lid

Add 2 to 3 gallons of water to the nutrient reservoir(bottom tote). Mix nutrients according to the needs of the plant you’re growing.

Adjust the pH as needed. If you’re using an aerator, go ahead and test it to make sure it’s working correctly.

Install the lid on top of the bottom tote. Slide the top tote onto the bottom tote. Make sure all the wicks drop down into the bottom tote.

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What Kind of Plants Grow in a Hydroponic Wick System

When you think about it, a wick system is a good simulation of conventional gardening. There is a soil-like media providing support to the plant and its root structure. The media retains moisture and nutrients that are absorbed by the root system.

Optimal Leafy Greens
Lettuce, Arugula, Boc Choy, Chard, Spinach, Kale

Optimal Herbs
Basil, Cilantro, Chervil, Chives, Dill, Marjoram, Mint, Oregano, Parsley, Watercress

Optimal Root Vegetables
Beet, Carrot, Fennel, Garlic, Raddish, Turnip

Technically, the system will grow almost any type of plant that performs best in well-draining soil. Even tomatoes, but let’s think about this for a minute.

There are a couple of factors to consider. Weight and convenience.

This is a stacking system. Tomatoes are large plants that can get pretty heavy, possibly heavy enough to make it hard to separate the two totes. Tomatoes and most other vining or bush plants need a support system such as strings, cages, or trellises. It’d be pretty inconvenient to move all that stuff in order to lift the top tote to refill the reservoir.

With that in mind, I’d recommend this system for growing smaller plants like leafy greens, most herbs, and certain root vegetables.

Small root vegetable varieties will work well in a small wick system like this. Larger root vegetables like daikon radishes or large carrots probably wouldn’t have enough depth.

The Best Wick Material for Hydroponics

Wondering what to use as a wick in a hydroponics system?

Wicking cords are the best wick material for hydroponics because of their durability and efficiency. These cords normally have a cotton center covered by a more durable nylon sleeve. The nylon sleeve increases surface tension, making this type of wick more efficient at moving water.

1/4 inch Capillary Wick Cord (50 ft.)
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02/18/2024 05:16 am GMT

If you don’t have wicking cords, don’t worry. People use all kinds of material for wicking systems. You can use torn-up cotton t-shirts, nylon pantyhose, basically, anything you have that will absorb and transport water.

Keep in mind that these materials won’t be able to move as much water, so you may need to use more wicks if you’re trying to soak a grow bed.

How Often to Change Nutrient Solution in a Wick System

The initial weak nutrient solution used to germinate plants will be useful for the first 2 to 3 weeks as the plants aren’t absorbing a lot of water or nutrients.

Once the first true leaves develop on the plants, replace the nutrient solution with a stronger solution. As the plants continue to mature they will absorb both water and nutrients faster and faster. The media will also begin holding nutrient salts.

From this point on it’s a good idea to check the reservoir level every 2 to 3 days. Top off as needed. Once you’ve topped off the solution 3 or 4 times, go ahead and completely replace the nutrient solution. Repeat this process until harvest.

Best Nutrients for a Hydroponic Wick System

I recommend using a concentrated one-part nutrient mix for two reasons:

  1. One-part nutrient mixes are as easy as it gets.
  2. Less measuring, less error. This system has a tiny reservoir (2-3 gallons). Small mistakes in measurements can make a large impact on the strength of the solution.
General Hydroponics FloraNova Grow - 1 Qt

One part hydroponic nutrient system

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FloraNova Grow is the one-part nutrient mix I use in my wick system, and I’ve been really happy with the results. One thing to note, this stuff is super thick. Shake it up aggressively before you use it. Also, make sure the lid is on tight before shaking it up.

Chris Cook started Happy Hydro Farm to share his passion for hydroponic gardening! Growing your own food is incredibly rewarding both physically and mentally. His mantra - "Take excellent care of your plants, and your plants will take excellent care of you."
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