Introduction to Ebb and Flow Hydroponics

To ebb is to recede, move away or reduce. Flow is a steady, continuous stream of something.

Ebb and flow systems are interchangeably called flood and drain systems, and that is precisely what they do. An Ebb and Flow system is essentially an automated bottom-water system.

Basics of Ebb and Flow System

Ebb and flow systems are a great space-saving way to grow nearly any crop you are interested in. A flood table can support small pots, large pots, or even a mixture of all sorts of sizes. The gentle, automated bottom watering of an ebb and flow table works for any stage of growth.

How Does an Ebb and Flow Hydroponic System Work?

An Ebb and Flow system uses a submersible water pump to flood the plants' root zones with nutrient solution. The water is returned to the reservoir using gravity or a second submersible pump.

The Process of Feeding Plants Using this System

In an ebb and flow system, you feed all of your plants during a flooding event. The nutrient solution is contained in the reservoir between flooding events and can be conveniently monitored and adjusted for all of the plants' needs. Through the use of quality meters, you can achieve near perfect nutrition that boost crop yields.

Choosing Your Ideal Ebb and Flow System

Ebb and Flow systems come in two flavors. The most common, most recognized and probably the most adaptable system is the Ebb and Flow Tray. You can grow small plants all the way up to anything that fits in your grow space as long as the table can support the weight. These tables can come in a variety of sizes, depths, and patterns of drainage channels on the bottom.

These tables are simply that, a flood table 2”-8” deep with a drain and a standpipe. The flood tray is suspended over the reservoir by simply putting the flood tray on a table or shelf. Having the reservoir under the flood table saves space and protects the reservoir and nutrient solution from light and heat produced by the sun or grow lights. 

This system uses a pump to flood the table, and the standpipe keeps the nutrient solution from filling beyond the desired level.  When the flood event is over and the pump de-energized, gravity drains the nutrient solution back into the reservoir. 

A more complicated system does exist for growing specifically larger plants. There is a common reservoir, commonly a 55-gallon drum or larger. The plants are all in their own individual planting sites. These planting sites are generally 5 gallons or so, and they are all strung together with a hose or pipe. The hose or pipe will lead to a “control box,” which is a sort of sump. The control box uses timers and pumps to flood the planting sites. When the flood event is over a timer tells a pump to return the water to the reservoir using the power of the pump. You can use Dutch buckets for this type of system since they are typically set up for irrigation or build your own from plastic buckets. 

This system is used extensively commercially. For larger crops where there is no headroom to spare, this system shines. Because gravity is not used in this system, the planting sites and reservoir can all sit on the floor. Another benefit is that you can use buckets for planting sites, which can be stacked and potentially even packed into your reservoir. This leaves your reservoir as the largest item as far as storage and shipping goes.

Tips to Choose the Perfect Fit for Your Setup

Ebb and flow systems with a flood tray are going to have a smaller footprint, but require more vertical space for your crops. A bucket plant site flood and drain allows plants more vertical space. It does take up more space, but larger plants can not be packed together like greens or seedlings that take advantage of a flood table system.

Setting Up Your Ebb and Flow System

Ebb and Flow systems will vary greatly in design and dimension but will be made up of the same components.

• The reservoir - An Ebb and Flow system is going to require a reservoir with enough capacity to hold at the very least 3x the volume of a full flood.
• The flood tray - (buckets in some systems) that holds the plants, and the nutrient solution when a flood is in progress. 
• Very sturdy table or rack for the flood tray - The weight of the plants and water in the flood tray during a flooding event will be surprisingly high. Water weighs in at 8.34lbs/gallon. 

The Pros And Cons of Ebb and Flow Hydroponic System

Advantages of Using an Ebb and Flow System

You can grow crops that do not do well with constant submersion as the conditions would demand in other hydroponic systems. You can use Ebb and Flow systems to keep conditions very similar in the root zone throughout an entire crop cycle. Some crops, such as herbs, can produce more potent essential oils when drought stressed.

With a flood and drain system, we can dial in the flooding events to happen just before the plants experience wilt. This sort of adaptability is excellent. When you couple that with the fact that an Ebb and Flow system can be anything from a flood and drain table to a rack with multiple flood trays stacked vertically to  larger plants in buckets or barrels with a control box, it becomes clear that flood and drain is a viable system adaptable to nearly every situation.

Drawbacks of Ebb and Flow Hydroponics

The versatility of ebb and flow hydroponics is impressive, but there are a few things to keep in mind. 

• Different mediums will require different management and the same media will require attention to flood frequency as crops mature and require more nutrient solution.

• Ebb and flow hydroponics flood all the plant roots. That water drains back to the reservoir and the nutrient solution is all mixed together again. This helps to keep the nutrient solution consistent but it also mixes pathogens, spores etc. This can lead to a complete infestation if we have problems with, say, root rot. Cleanliness is the key to success in any hydroponic grow. 

• We must maintain a clean environment above all else; in hydroponics, that is the first and foremost priority.

Choosing Your Grow Medium in Ebb and Flow Hydroponics Systems

Exploring Different Grow Medium Choices

You can flood and drain in almost any growing medium. I like to think of the medium as the buffer that regulates irrigation frequency. A very common medium is clay pellets that drain readily and allow for multiple flooding events per day. Coco coir and rockwool require fewer irrigation events to produce feast to famine conditions that will help encourage rapid, healthy growth in the root zone.

Tips To Choose The Right Medium For Your System

Let me reiterate: you can use any grow media your heart desires, but that may come with some limitations or special management. 

When we use clay pellets, straight perlite, gravel or similar materials, drainage is excellent. These materials can hold a certain amount of water but we are using these materials for their quick drainage. Some of these materials can be sterilized and are, therefore, quite economical. These mediums are hard and solid, and after an initial rinse, they do tend to keep your nutrient solution cleaner as it floods and drains from the media in your containers. These are the mediums that are going to require more frequent irrigation events.

Coir, and rockwool are more fibrous and have a much softer feel. They tend to hold more water for a much longer amount of time and, therefore, will reduce the need for irrigation. These mediums are more of a bottom watering technique. You will flood to a shallower depth to prevent disrupting the media or overwatering. Overwatering will quickly lead to root diseases taking hold in the system. In hydroponics, our nutrient solution is being delivered to all the plants in the system simultaneously, so a disease that affects one plant can quickly spread. 

My suggestion is to experiment. Try different media mixes, grow out plants with several mediums and compare, and use different irrigation schedules and varieties of crops you produce (some will behave differently than others.) 

The point is there are no rules, and it is not often in life that we receive this kind of bandwidth. Your mileage may vary, but please have fun.

Maintaining your Ebb and Flow Hydroponics System

Importance of Cleaning the System Regularly

As with any hydroponics system, cleanliness is our foremost priority. We want to flush the system as needed and always deep clean between grow cycles. You want to get in the reservoir with a brush and scrub. Use vinegar for mineral deposits. Hydrogen peroxide is a wonderful cleaner and it even breaks down to oxygen and water. You do not want to get it on your skin. I have used hydrogen peroxide in aquaponic systems in certain circumstances, and while we were quite conservative with the dosage, it did help, and we lost zero fish.

Controlling pH and EC levels for Optimal Results

There is no hydroponic system that can deliver reliable results without a consistent pH and/or EC. You need a quality EC meter and a pH meter. This is an investment that is going to help you to feed your plants accurately. We want the plants to have all the nutrients they need, and we also want to ensure that we have the pH in a range that will keep those nutrients and minerals accessible for the plants' roots to absorb. 

If we are out of the ideal window for pH, we may have deficiencies showing up in our crops, even though we have spent the money on the fertilizer and have kept the EC at the correct level! 

Nutrient lockout can occur when certain salts build up in the growing medium or our nutrient solution. This can happen when we need to flush our system more often. We can also see plants get burned from excessive fertilizer. 

As you can see, we need both measurements to dose fertilizer accurately and for the fertilizer to be accessible to the plants.

Is an Ebb and Flow System Right for You? 

You can grow nearly every crop in an Ebb and Flow system. The systems vary greatly in size and design and can adapted to nearly any grow room, greenhouse or garden. A bucket system is more modular but also requires more equipment. Both systems can be managed to use different grow mediums and are available as kits ready to be easily assembled by the most novice hydroponic grower.

Frequently Asked Questions (FAQ)

Do I need an air pump? 

YES! The nutrient solution is in your reservoir 99%+ of the time. In an ebb and flow system the water is only disturbed when it is draining back into the reservoir during/after a flooding event. This is not enough aeration for your crops.

Does my water pump size matter? 

It does to a point. Too slow of a pump is not really an issue, it may take longer to flood your tray or bucket sites. Taking too long is not the end of the world, as long as we are not talking hours to flood. Too much pump can, however, be an issue. This is not a huge issue if you are using clay pellets or gravel. When we are using coir, soil or perlite straight, we want to be sure to flood our tray slowly. If we flood them to quickly they can float and tip over because the nutrient solution is flooding the tray faster than the medium can be saturated. 

How big of a reservoir do I need? 

You need a reservoir that has enough volume to flood the flood tray or the planting sites and still retain enough water in the reservoir to keep your pump completely submerged. A submersible pump will overheat very quickly if not submerged in water.

What is needed for an ebb and flow system?

All Ebb and Flow systems require a submersible pump, a timer, an air pump with air stone, and a reservoir.

You need a flood tray, sturdy table or rack and a reservoir for a flood tray system. A bucket style system is going to require buckets, a controller bucket, and all of the tubing to connect the buckets in series.

If you are not an experienced hydroponic grower, Ebb and Flow kits are sized appropriately and have all of the equipment you need to get setup, and growing. There is sure to be a style/ size that will fit your needs and you will not have to spend the time sizing and sourcing all of the components for your system. 

How many plants can I grow with an ebb and flow system?

You can have as many plants as your can fit on a flood tray. Your flood tray can have few large pots or many small pots. You can plant smaller plants like greens in a solid sea of green covering your entire tray.

In a bucket system you can have as many sites as your reservoir will allow you to flood. You must have enough water leftover in your reservoir to keep the pump submerged, but there is no limit to how large you can go. 

Can I grow flowers in an Ebb and Flow system?

Yes, hydroponic systems work especially well for growing edible flowers because you can control the environment completely and grow pest free flowers. You can learn more about Growing Edible Flowers Hydroponically in this article. 

Are Ebb and Flow Systems Different from Flood and Drain Systems?

These are synonyms. They are one and the same.

Want to learn more about the basics of hydroponics? Check out Hydroponics 101: A Beginner's Guide to Efficient and. High-Yield Plant Growth.