Once you’ve had a harvest or two in your garden, it’s worth considering some hydroponic methods and techniques to continue improving your process and potentially save time. One of those techniques is called “Ebb and Flow.” It is sometimes referred to as “Flood and Drain” or “Running Flood Tables.”
Ebb and Flow is an intermediate technique in the world of hydroponic agriculture. It’s not too complex to set up, and it can run itself with a good system in place. Once set up, you can focus on sanitation, stress training, and other aspects of your grow instead of regularly worrying about water. There is no single attributed inventor or specific origin of Ebb and Flow systems; they evolved over time as understanding of hydroponics and the necessary technology increased. We’ll walk through just what these systems entail below and cover some pros and cons of running Ebb and Flow.
What is ebb and flow hydroponics for cannabis?
Hydroponics, in general, have been used throughout history. In fact, the Hanging Gardens of Babylon are thought to be an early type of hydroponic system. The Babylonians were onto something good because hydro, especially the Ebb and Flow systems, are here to stay. They are widely used and loved by cannabis and general agriculturalists.
Ebb and flow
Ebb and flow is a hydroponic technique that falls into the “soilless” category of hydro. It’s a low-cost, highly efficient system with semi-automated processes. The system can be set up for micro grows and scaled up to full-scale professional operations.
Plants are placed in pots or directly in inert media like clay pellets, coco coir, and perlite inside trays. These trays sit above and connect to a water reservoir. Throughout the day, a pump in the reservoir floods the table above with nutrient-enriched water. Tables are allowed to flood for ~15 minutes, depending on plant size and other environmental factors, before the water drains from the table back into the reservoir.
Check out the video below for a quick visual guide about how the ebb and flow method works for weed plants.
Matthew DeBacco is a Professor of Agronomy (MS) as well as Plant Pathology and Horticulture (BS), who teaches several courses on the Horticulture of Cannabis at the Department of Plant Science and Landscape Architecture at the University of Connecticut.
Be sure to like and subscribe to his channel: https://www.youtube.com/@DeBaccoUniversity
This is a cool process because unused water that would normally become runoff in a grow is routed back to the reservoir for use at the next feeding. When flooded, the roots of the plants are exposed to the nutrient solution; then, as the table drains, they can dry out. This keeps the root zone well oxygenated and means you don’t need to worry as much about oxygenating water because plants will be exposed to oxygen between each feeding.
A side view of how an ebb and flow setup works
I mentioned that this process is semi-automated, which is an important distinction. Some work is still involved; Ebb and Flow is not “fully” automated, and few home/affordable systems are. While a timer and pump handle the actual watering, the water reservoir itself needs to be cleaned and maintained regularly, as well as the pump and any piping and tubing used in the system. This sanitization is generally necessary in hydroponic systems to prevent disease and maintain system efficiency and nutrient quality.
Observation
The other piece of the puzzle that requires your attention in an Ebb and Flow system is observation. Monitor the pump, timer, and setup for any leaks or signs of failure. A failed pump or broken timer may end your harvest early. You can do this during sanitation, but it still needs to be done while the system is running.
While the Ebb and Flow method provides many benefits, it is not 100% set-it-and-forget-it. Like everything in cannabis cultivation, it requires that human touch (for now).
What are the pros and cons of an ebb and flow technique?
Let’s break down the benefits and drawbacks of Ebb and Flow. The system is extremely popular and proven, but consider it alongside your goals as a cultivator, budget, and space constraints.
Pros of an ebb and flow system:
Ease of Use: Ebb and Flow systems are relatively straightforward to set up and operate. While traditional growing may be the best place to start as a beginner, these systems are a close second and definitely a good start for beginners who know they are going Hydro.
Automation: Your watering phase can be automated and consistent with timers and a few test runs. This means the only work needed would be changing the reservoir water regularly and sanitizing the system. You can be sure your plants are receiving equal amounts of nutrients this way while ensuring the roots get oxygen as well in between waterings.
Versatile: These systems are extremely versatile and can help you be successful as a cannabis cultivator in any indoor situation. With the ability to scale up or down, you can easily adapt systems to fit your unique garden.
Oxygenation: As mentioned previously, Ebb and Flow systems contribute to healthy root growth by providing periods of “drought” between waterings that give roots the oxygen they need. This can be an issue in soil systems and other hydro methods that would have the roots submerged constantly or for longer periods.
Cost Efficient: You can purchase Ebb and Flow systems as an all-in-one kit, but the true efficiency can be found by building the unique system you need. Unlike other hydro methods, the whole technique doesn’t require an extensive list of equipment. (We’ll review that list in a moment.) The water used is also recycled back to the reservoir, reducing the costs required for the garden.
A simple and inexpensive ebb & flow system kit. Ready to use out of the box by Platinium Hydroponics
No cultivation process is perfect and without tradeoffs; Ebb and Flow is no different. Here are a few issues with the technique to be aware of.
Cons of an ebb and flow system:
Root Disease: This process’s flood/drain cycle can create conditions that allow root pathogens to thrive and potentially lead to diseases like root rot. During the flood phase, your system may get pockets of stagnant water that become home to harmful microorganisms. Over time, organic material from the plants is returned to the reservoir and can be fuel for problems if not cleaned regularly. When draining the tables, anaerobic bacteria that thrive in low-oxygen environments can also develop if you’re not draining fast enough or if your media is retaining too much water.
Failure Points: There are a few failure points in Ebb and Flow systems that can really ruin your day as a cultivator. Things like pump and timer malfunctions can lead to over and underwatering, which can, of course, harm or even destroy cannabis plants. Never completely trust the system; it’s still important to check on things and to keep some redundancies on hand, like an extra pump and backup timer.
Sanitization: Hydro always sounds great and looks easier when first considering the techniques, but like everything in this hobby, we believe cleanliness is next to godliness. Cleaning a hydroponic system is work; there’s no other way around it. You must maintain the reservoir, pumps, and piping to prevent disease and keep the water quality and nutrient density on point.
Nutrient Imbalance: This potential drawback can be crucial for smaller systems as smaller reservoirs of water can imbalance faster than larger ones. An imbalance can tilt your nutrients one way or the other and impact plant growth at any stage. Checking your nutrients and keeping the reservoir refreshed regularly is important.
No Precision Control: Because of the ease of use here (you’re literally flooding trays and letting them drain back repeatedly), it’s more difficult to fine-tune nutrient delivery and pH than other systems like Drip or NFT. Also, if you have plants of different cultivars in the same tray with different moisture and water requirements, it’s hard to address them without building a second ebb and flow system to cover the differences.
How does ebb and flow differ from other hydroponic methods?
You’ve seen the good and the bad with Ebb and Flow. Now, let’s compare and contrast it against other hydro techniques.
1. Deep Water Culture (DWC): DWC is a “continuous-flow” system, whereas Ebb and Flow is cyclical. In other words, in DWC, your roots are constantly exposed to nutrients and water instead of only during the feeding phases. A DWC system will require properly oxygenated water. For more info on DWC, check out our guide here.
2. Drip Systems: Instead of approaching the hydro solution from the roots, drip systems are top-fed using irrigation hoses run into each plant. Users of this method need to be careful about adjusting the flow rate of drip systems and ensuring their roots dry out on occasion. Ebb and Flow, as we know now, will intermittently flood the roots instead. For more info on hydroponic drip systems, check out our guide here.
3. Aeroponics: Aeroponics systems are much different than Ebb and Flow in that the roots are suspended in air in closed pipes or reservoirs where a nutrient solution is sprayed in a fine mist periodically onto the roots. This misting technique is unique to aeroponics and brings a host of other issues, making it one of the more difficult hydro techniques compared to the ease of ebb and flow. For more info on aeroponics, check out our guide here.
4. Nutrient Film Technique (NFT): NFT is an interesting technique that continuously flows a small amount of nutrient solution over the roots in sloped channels. Ebb and Flow fully submerges the plant roots in a nutrient solution, albeit intermittently. For more info about NFT, check out our guide here.
5: Kratky Method: Kratky changes the game in hydro by relying on a static nutrient solution and water reservoir. It’s the simplest hydroponic system and often the cheapest and easiest to manage, as you won’t be flowing or moving any water. For more info about Kratky, check out our guide here.
6: Wick Systems: Wick systems utilize a wick to passively draw water up from a reservoir vs the active nature of flooding the tables during Ebb and Flow. For more info about Wick Systems, check out our guide here.
What are the different types of setups for ebb and flow systems?
Ebb and Flow hydroponics may be a simple technique, but many different ways exist to implement it in practice. Choosing which one depends on the available space, plant quantity, budget, and the cultivator’s preference. As you’ll see below, there are many ways to make an Ebb and Flow system perfect for your grow and goals. The number of trays and reservoirs used in the system can change some of the concerns and materials needed as well as the results. Single-tray setups will run a single reservoir, whereas multi-tray setups will connect to a larger reservoir or series of reservoirs. Keep in mind that with more reservoirs, you add some redundancy to your system. This can prevent a system failure from taking out the whole crop, but the tradeoff is that you have to worry about each individual reservoir. Besides that, multi-tay or multiple reservoirs are mostly used for large-scale and commercial grows.
Various Ebb and Flow setups, ranging from small to larger grows.
While many use pots and containers in these hydro systems, the plants themselves can be placed directly in a tray of inert media like clay pellets. This is often used for seedlings and early veg but could be used throughout flower. Aeration can be altered in Ebb and Flow setups as well. By adding airstones to the reservoirs or the flood tables themselves, you can be sure to provide an oxygen-rich solution.
Another variation of this system that I’ve used is a mobile reservoir. Essentially, it is a big ol’ water tank on wheels that can be moved around the grow to run Ebb and Flow in different rooms. For more good tips and tricks about the growing with various water methods, download our all-in-one Grow Bible.
How to set up an ebb and flow system
An illustration of a setup of of an Ebb and Flow system
With all the variations on Ebb and Flow discussed in the last section, you can see that there isn’t really a single or best way to set up Ebb and Flow. However, a simple example we can use to teach the basics is the single reservoir single tray solution. It may be perfect for a little home grow.
Materials for an Ebb and Flow cannabis setup:
Reservoir with Lid
Tray (Flood Table)
Rubber piping (diameter depends on your setup, plant count, and pumps)
Water Pump
Timer
Complication of materials you need to create your own Ebb and Flow system
Guide:
1. Start by drilling two holes into the reservoir. Then, drill two holes into the tray itself. These can be lined up directly if using PVC piping or offset for more flexible piping. It’s wise to keep these fairly close to one another to prevent any standing water that may occur in flexible piping.
2. Connect the reservoir and the tray with PVC or other piping. The pipe should extend up into the tray above the level of water you expect to flood the table with. This is called the overflow tube, and it prevents you from accidentally flooding your grow space. Any water that exceeds the root zone will drain through this back into the reservoir before overflowing.
3. Now, connect the final set of holes with PVC or other piping that extends down to the bottom of the reservoir. This is both the flood and drain line for your system.
4. Attach the pump to the tubing from the previous step and place it into the reservoir.
5. Set up your pump timer. Timing is hard to generalize as it depends on your tray depth. I’d recommend running the pump with a time clock to see how long it takes to flood and start with that as your number. The industry is quick to recommend 15-minute floods and 15-minute drains, but be careful with generalized numbers. Remember, we don’t want to flood the grow room, only the tables.
How to maintain and care for your plants using an ebb and flow setup
All of your plant maintenance at this point will mirror indoor plant care and methods found in our Grow Bible. The difference is that you need to monitor the ebb and flow system while keeping it clean.
You must do some trial runs on your plants to fine-tune the watering interval for your hydro setup. This can again depend on the environment and other variables, but you’ll want to flood the plants between 2 and 4 times a day. If your medium is slow-draining and the environment is humid, consider flooding less, but if the environment is warm and dry with a fast-growing medium, flood more.
Check out the video about how ebb and flow irrigation works for cannabis plants below. The video was created by professor DeBacco from the University of Connecticut. Just as with the previous video, don’t forget to like and subscribe to his channel: https://www.youtube.com/@DeBaccoUniversity
Flood your cannabis plants more during the vegetative stage
In general, you’ll want to flood once more during veg than you do in flower to go along with the increased lighting that plants get during veg. The speed of the pump, the size of the tray, the height of the pots, and more can all tweak these numbers one way or the other. Start carefully and stay with the system while it’s running to time the flood and drain down to the right interval for your grow.
My final thoughts on using an ebb and flow system
Ebb and Flow hydro is awesome; it’s one of my favorite methods, with the other being Drip. When it comes to ease of use and flexibility, it’s unparalleled. I prefer hydro over traditional methods, but I may be a little biased since my most successful grows used hydroponic systems. With Ebb and Flow, you can get all the hydro with a good balance of maintenance and budget.
The master grower I learned from was also adamant about allowing the roots to thoroughly dry out. While you can use sensors, he would have me lift the pots to get a feel for what they are when dry vs. fed.
It may sound arbitrary at first, but working with your plants over time, you’ll develop some quick methods to check on things, or you can get a soil moisture meter if you’d like to get right to the numbers. If there’s anything else you’d like to know about Ebb and Flow Hydro or if you’ve also had success with this method, please leave a comment below or reach out. Keep on Growing!
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