The wick system is the simplest of all the hydroponic system types. That's because it doesn't rely on pumps or aerator systems, thus doesn't use electricity. However some people still like using an optional air pump in the reservoir. Since it doesn't need electricity, it can be used anywhere. The wick system is an easy type of system to build when first learning hydroponics.
What you need to build a wick system:
A container to hold the plant and growing media A container for the water/nutrient reservoir Wicking material such at coco coir, vermiculite, or perlite An absorbent material like felt or a wicking rope How the wick system works is just like it sounds, it basically just wicks up nutrient solution from the reservoir to the plants using the process of capillary action. Meaning it sucks up water to the plants through the wick like a sponge. The container (with the plant) in it basically sits right above the container used for the reservoir. The wick hangs down into the bucket and draw the nutrient filled water up to the plants roots.
Downside of wick systems
The downside to a hydroponic wick systems is they don't work well for larger plants that need more water. They are more suited for non-fruiting plants, like lettuce and herbs. While the wick does suck up moisture to the plants roots, the larger the plant is, the more water it will need to take up. Fruiting (tomatoes, peppers, cucumbers, etc) plants will need even more water to support the growth of all the fruit it produces. Wick systems also has the disadvantage of being less efficient at delivering nutrients. Heavier feeding plants may need nutrients faster than the wicks can supply them to the roots. Lettuce and herbs are generally light feeders, while plants like tomatoe's, peppers and most fruiting plants are heavier feeders. Wick systems also don't absorb nutrients and water evenly, and the wick can’t tell what nutrients the plant needs. The plants takes what it needs, and leaves the nutrients in the growing medium. This can eventually cause a toxic buildup of mineral salts in the growing media. Flushing the excess nutrients from the growing media with plain fresh water should be done regularly every week.
The wick itself is probably the most important part of the wick system. Without a good absorbent wick the plants would not get the moisture and nutrients it needs. You will likely need to do some testing of different materials to see what works best for you. When looking for a good wicking material, you'll want to use something that's absorbent, but is still resistant to rotting. You must wash the wick good before using, can significantly improve the wicking ability of most materials. Some common materials people have used for wick systems are: fibrous rope, mop head strands, cotton rope, strips from old clothing or blankets etc. etc. Make sure to use enough wicks to support the plants water usage will depend greatly on how you build your wick system. The type of plant your growing, and the growing medium you use. You'll likely need at least 2 or more wicks unless it's a real small system. Also the shorter up the wick the more water and nutrients that the plant can uptake. You will need a very absorbent growing media to hold moisture. Some of the most commonly used growing media's for wick systems are things like perlite, coco coir, vermiculite, or water absorbing polymer crystals can be used.
The wick system reservoir needs to be large enough to not run dry. You want the solution to remain high enough so it doesn't have to travel far to get to the growing media/root zone. You'll want to top off the reservoir with fresh nutrient solution as needed. Will need to clean out and change completely occasionally. Because algae and/or microorganisms will grow in the rich water, especially if exposed to light. The wick does not absorb the nutrients evenly, so there will be a build up of excessive salts over time. You will want to flush the system with plain fresh water regularly to prevent a problem from developing. Probably something like about every couple weeks. If this isn’t done, your plants will suffer.
Optional air pump
Using an air pump with an air stone isn't necessary, however it can be beneficial. The roots will be able to absorb oxygen from the air pockets in the growing medium, they also absorb dissolved oxygen directly from the water itself. Helping to aerate the water, the rising bubbles keep the water circulating. Keeping the nutrient solution water moving keeps the nutrients evenly mixed up. Without it the nutrients will settle to the bottom over time. However, if you using an air pump anyways, you may want to build a deep water culture system instead.