- Weedguru Higher
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CHOOSING A HYDROPONIC SYSTEM
Numerous different types of hydroponic systems are suitable for mj cultivation. Choosing your "best" system will depend on your individual growing environment and expectations. Some types are better for growing large plants, as in a closet grow, while others are best suited to growing smaller plants, like those in a ScrOG (Screen Of Green) or stealth environment. For example, you probably would not consider NFT (Nutrient Film Technique) if you intended to grow your plants to six feet in height, since the NFT system is designed primarily for smaller root system crops, and the table will tend to reduce the height available for plant growth. To grow a larger plant, you would likely be interested in a Bubbler or Pot type Ebb & Flow. On the other hand, NFT is an excellent choice for ScrOG growers.
Hydroponics offers you a vast opportunity for creativity. Most of the systems are relatively easy to build for an average do-it-yourselfer. By building your own system, you can save a lot of the initial investment (although it still isn't cheap). You can combine features of systems that suit you and your grow best. Or you can buy any of these systems as complete systems from hydroponic manufacturers if you haven't the time or inclination to design and build your own. Complete systems are commercially available that contain everything you need, and some of them are very good quality, potentially lasting for many years.
So take your time and give some more thought to your garden. Read about the various types of hydro systems available and check out the example pages before making a commitment. Check the discussion boards on the Internet for even more ideas. A little planning ahead of time will assure you of a successful garden the first time around.
(Note: We will not be considering any hydro systems NOT suitable for growing mj. Very small NFT's, vertical, bag culture, and passive hydroponics are ideal for smaller type crops, but not for any form of marijuana, so we have intentionally left them out).
Five main types of hydroponic systems are popular and suitable for growing marijuana. They are all active, recirculating nutrient types:
* NFT (Nutrient Film Technique),
* DWC (Deep Water Culture) and it's little brother Shallow Water Culture,
* Ebb & Flow,
* Drip Systems, and
NFT (Nutrient Film System)
NFT (Nutrient Film System) was one of the first real, successful hydroponic systems. It was originally designed to be cheap to set up and inexpensive to run on a large scale. This type of setup is ideal for growing small-to-medium sized plants, as in a ScrOG grow. NFT features excellent growth rates and low maintenance.
Many variations of the original NFT setup exist. The original setup had "gullies" or channels (very similar to rain gutters) arranged on a slight slope of about 1:40 (25 mm drop per meter length), up to 15 or more meters long. A common variant (although not a true NFT) uses PVC pipes, 6-8 inches in diameter with holes cut in for the plant sites for the "gullies". While these gully sets are very commonly used for lettuce, strawberries, herbs, and other short term crops with minimal root networks, most mj growers prefer a table type of setup, as this affords the root systems much more room to grow. A chicken wire screen is easily mounted over the top of the table for supporting and training the plants into the ScrOG.
Operation of the NFT table is simple: A small submersible pump circulates the nutrient solution from the reservoir to the manifold on the raised side of the table. The manifold has adjustable drippers to regulate the flow of nutrients to an even and thin "film" (generally less than 1mm in depth), which flows down the table and around the roots of the crop. Nutrient flow times can be adjusted by a timer, although many gardeners prefer to leave the pump running 24/7.
Rockwool is a commonly used media in NFT systems. It gives the plants support until they reach the screen (or other support) height. It is not uncommon for the roots of the plants to grow together into one solid mass over the entire surface of the table as the growth progresses, which in turn gives the plants even more support.
Plenty of oxygen is available to the roots as the nutrient flows down the tray, as the roots are always exposed to air and never completely submerged. That is the central idea behind the "film" - the roots are not submerged in nutrients, allowing oxygen from the surrounding air to contact them at all times. As in all hydroponic systems, oxygen must be readily available to the roots. This is critical to plant growth.
As with all active hydro systems, NFT is susceptible to power outages. NFT is perhaps a bit more susceptible than most because there is little or no media to act as a buffer and retain moisture. Should the power to the pump be off for more than a few hours, the entire crop may die from lack of moisture to the roots. A gravity-driven backup nutrient delivery system or backup generator is necessary where power is not reliable.
The NFT table also relies on an even nutrient flow over the surface of the table for successful operation. Solution cannot be left to accumulate into puddles as this will promote root rot. Dry areas must likewise be avoided for obvious reasons. Various types of mats are available to help spread and keep the flow down the table even.
Drippers or flow regulators and drains occasionally get plugged with debris or root parts. It's important to check and clean these regularly to insure the proper nutrient flow down the table. A properly designed system will enable you to disassemble these components for easy inspection and cleaning.
Tables, like these used in NFT and Ebb & Flow systems, are usually standard sizes (common are 36"x36"x4" or 43"x19"x8"). Rockwool slabs fit neatly inside the table.
Taken to an extreme, that is if the nutrient flow becomes deeper than just a film and covers the roots, the NFT system approaches the characteristics of an Ebb & Flow or Dutch Pot system.
Not shown is a cover over the entire table, with holes for the plants to protrude through. The cover is necessary to keep light from encouraging algae growth in the nutrient solution
Deep Water Culture
DWC, or Deep Water Culture (aka "Bubbler", "Bubbling Bucket", "Aquafarm", or "Air Pump System") is arguably the best hydroponic method for growing medium to large sized plants and other longer-term crops. Plus it's one of the easiest and cheapest methods around, especially for the do-it-yourselfer.
The concept is simple: A netpot filled with media (lava rock, clay pellets, etc.) sits in a hole cut in the lid of a 5-gallon plastic bucket. Air is supplied by a small aquarium-type pump to an air stone submerged in the nutrient solution. The nutrient solution level is kept about an inch or so above the bottom of the netpot, but can be fall below as the plant's roots grow down into the solution.
While some consider the DWC to be a passive system because of it's simplicity, it is really an active system, with the nutrient solution being constantly oxygenated and agitated by the constant bubbling effect. This constant aeration of the solution and roots produces very rapid growth rates and is the key to DWC.
Because of the large amounts of oxygen constantly being dissolved in the solution, algae thrives in bubblers. The bucket must be light-proofed if it is not already black, possibly by painting it black or some other method. The top and surface of the media should also be covered with black plastic to reduce light penetration into the bucket.
Large air pumps are not necessary; the smaller fish tank variety commonly available for US$25 or less work fine for a single bucket. Many growers prefer two-outlet air pumps, and use two six-inch air stones in the bucket. Larger air stones will increase circulation and dissolved oxygen in the reservoir, promoting even better growth. Air stones do get plugged up and need cleaning with a toothbrush or replacement every few weeks. As soon as you see the air diminishing, clean or replace the air stone (about US$2 for a good one).
Netpots must be strong for bubblers. The plants will grow rapidly, and the (wet) root mass plus media plus green leafy growth will be supported solely by the netpot. Swimming pool skimmer filter baskets work great as netpots - they are reusable, and cheap. Likewise smaller 3.5-gallon buckets with holes drilled work well as netpots.
Try not to use buckets smaller than the 5-gallon size for the reservoir. Smaller buckets don't have enough capacity to buffer changes in solution as the plant grows and nutrient uptake increases. You would be spending all your time trying to keep the solution within bounds, and that increases the chance for mistakes and ultimate failure. In general, all hydro systems perform better with larger reservoirs for this reason.
DWC is only slightly sensitive to power loss, as the large reservoir offers a degree of safety to the roots drying out. The plants can survive for at least a few days without the air pump functioning. Of course, extended periods of outage may damage the crop from root rot.
A variation on DWC is - you guessed it - SWC, or Shallow Water Culture. It's essentially a scaled-down and miniture version of DWC. SWC is ideal for stealth cabinet grows or other environments where height may be limited.
Nutrient and pH management are just as critical with DWC and SWC as any other hydro system. Monitor solution level, pH, and EC (or TDS) and adjust as necessary.
Ebb & Flow
Ebb & Flow (aka "Flood and Drain") systems are also commonly used for growing small to medium-sized plants. There are two main types of Ebb & Flow systems - the "table" (by far the most popular) and a newer "bucket" system. Both systems are based on the same concept: two cycles alternately supply nutrient and oxygen to the root system. Ebb & Flows are capable of very rapid growth, however they are very sensitive to power fluctuations and moderately complex electrically and mechanically.
Here's how it works: The submersible pump operates by a timer and fills the table (or pot) with nutrient solution - the "flood" cycle. The roots absorb nutrients from the solution and are thoroughly wet. After a pre-determined interval, the pump stops or a valve opens and the nutrient flows back into the reservoir - the "drain" cycle. During this time, the roots are able to absorb the all-important oxygen. A typical cycle might be one hour: 15 minutes to flood the tray with nutrient solution, and 45 minutes for the roots to absorb oxygen.
Ebb & Flow systems should always incorporate some type of overflow mechanism. This is simply a tube set at the overflow height of the table, leading back to the reservoir. It's purpose is to guarantee the table is filled with solution and all the roots are flooded before draining. The pump can run and recirculate the nutrients, which improves aeration.
Grow media can be rock wool, lava rocks, gro-rox, expanded clay pebbles, perlite, vermiculite, or whatever you like. Filters may be necessary to reduce the chance of plugging up the plumbing or pump, as with any system. Support for maturing plants can be the screen (ScrOG) or other means.
Again, the larger the reservoir, the better. Given a 30-gallon reservoir and a 3' x 3' table, you could conceivably get by with maintenance only two or three times a week. And as with all hydro systems, the reservoir should be an opaque food-grade plastic to reduce algae growth and minimize nutrient contamination.
An interesting variation on the Ebb & Flow table are the relatively new "pot" or "bucket" systems. These operate on the same principle as the Ebb & Flow table - flood and drain cycles - but incorporate two pumps and valves alomg with the timer in a separate "controller" enclosure, connected to the grow pots and reservoir with irrigation tubing. The controller manages the nutrient flow in and out of the pots, filling them to a preset level before draining them back into the reservoir. It's essentially an Ebb & Flow system without the table.
With this system, it may be easier to grow larger plants since the height of the table is not a limiting factor. The pots are also able to support larger plants in more (and heavier) grow media.
These systems are moderately more complex than any of the others due to the two pumps, valve, and timer arrangements, and are not easily constructed by DIY types.
Drip systems (aka "Dutch Pots", "Aquafarm", or "Drippers") are very common because they are simple and effective. They are also simple and cheap to build, if you want to experiment on your own. Drippers work very well for medium to large plants, as well as long term crops.
Drip systems are probably most similar to the Ebb & Flow systems. Drippers run the pump on a timer, pumping nutrient into the pots, where it immediately drains back into the reservoir. After a preset interval, the pump stops, letting the remainder of nutrient drain into the reservoir and the roots absorb oxygen.
Timing is also similar to the Ebb & Flow - typically 15 minutes pump run time, and 45 minutes off, although this is entirely up to you. Additionally, the dripper heads are individually adjustable so you can tailor the flow to the individual plant. This is a great advantage where you may have both seedlings and mature plants on the same system.
There exists another type of dripper where the nutrient flows into the pots very slowly - and does not return to the reservoir. Instead, the nutrients are evaporated, used by the plants, or run to a drain. This is termed a "run to waste" system, and although somewhat successful, it is not very popular. Salt buildup from the nutrients is very difficult to control.
Drippers are somewhat simpler than the Ebb & Flow in that there is no need for an overflow - the nutrient is constantly being drained back into the reservoir without the use of valves. Although there is still the possibility of tubing or pumps plugging up, it is reduced in the dripper. Redundancy in the containers also helps improve overall reliability.
Aeroponic (aka "Aerospring") systems have the highest oxygen-to-solution ratio and therefore the greatest plant growth rates of any hydroponic design. However, they are a little more temperamental than the other types and require a little more care due to the smaller reservoir capacity and intricate sprayer system. These are favorite systems for the do-it-yourselfer and for those really interested in spending time tinkering with their gardens. These are best suited to small to medium sized plants, as larger plant's root systems will quickly overwhelm the reservoir.
Conceptually, areoponics is simple. The plant's roots are suspended from the netpots over the nutrient solution in the reservoir. Tiny sprayer heads, or "emitters", attached to a single PVC pipe running down the center of the reservoir, continuously spray a fine mist of nutrient over the roots. This affords the roots the opportunity to absorb both nutrient and oxygen simultaneously, resulting in the best growth rates of any hydroponic system.
Pump pressure must be regulated so that the spray is not a sharp, high pressure stream which could damage the roots. A fine spray is what you're after here, just enough to keep the roots damp.
Rubbermaid or Roughneck containers (30 gallon capacity or more) are commonly used for the reservoir, with holes (usually six) cut into the lid for the netpots. The submersible pump supplies the pressure to the spray heads, then also can pump the nutrient out of the reservoir via the drain valve for easy solution changes and cleaning.
The fine spray heads are prone to plugging and should be checked often. It's important that a fine spray, or mist, be functional at all times. As already mentioned, the small reservoir capacity of only five or six gallons make the aeroponic systems sensitive. Nutrient levels and strength, and pH must be checked regularly. Obviously, this system is very susceptible to power outages - a backup dripper system may be desirable in areas with unreliable power.
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