Episode 10- Building An Aquaponics System: Media-based systems, Basics of Plumbing and Drainage
Previously, we discussed system design and meeting your present and future needs.
Today we’re going to talk about media-based systems, plumbing, drainage and even a bit about bio-filtration.
You’re going to get some great insight into our experience with media based systems throughout the podcast.
A Quick Refresher: Media
Media based systems are systems where you grow plants with the help of some type of media as opposed to media-free, or media-less techniques like aeroponics.
Often the media acts as a biological and mechanical filtration material. The media can remove solids, transform chemicals, and act as an anchor for plant roots.
Most home and hobby systems are media based systems.
As you know, we use Matrix Media to accomplish these goals and much, much more.
Types of Media
Knowing the types of media available will help you make an informed decision about what technique is best for you
- Crushed Granite
- Pea Gravel
Our favorite in this category is 3/4 inch crushed granite. It’s easy to acquire, easy to clean, and has good percolation. Having said that, it’s not effective with root crops and it can be hard on your hands.
Sand is another aggregate, though not one that we recommend. Sand performs alright at first but because there’s not much pore space, it fouls, goes anaerobic, and you end up with root issues- bad news!
Stay away from pea gravel and things like that. 5/8 inch is the smallest you should go with aggregates.
Another think to stay away from limestone. You can test gravel for this quite easily: drop it in an acid like vinegar. If it bubbles, it’s probably basic.
Fibers are the third type. An example is the Matrix Media that we use.
I love this because it has excellent Specific Surface Area and great percolation.
Let me explain why this combination is special: Something you want to remember is that as the size of the particle grows, the lower the surface area is. But the smaller the particle gets, the more it clogs and fouls. This means that high surface area means fouling, and low surface area means fewer microbes.
With aggregates, you have to choose one over the other. Fibers have the best of both worlds: good percolation and good surface area. It’s also usually lightweight. Fibers are definitely worth pursuing.
Organic Material Media
A common question is “Why not organic materials? Why not peat, why not coconut core?”
The answer is that you need something that won’t decompose.
There’s so much nitrogen and microbial activity in your system that the microbes in your system will consume your nitrogen to break down the carbon of organic materials. Then they start competing with plants (which keeps nitrogen low) and as the media is decomposed, it compresses and percolation goes down. Eventually it fouls and you end up with an anaerobic mess.
Stay away from organic media. Even if your mixing perlite, it’s still not worth the trouble.
Choosing a Container for Media-Based Systems
In a media based system, you move water from a fish or sump tank and you dump it into a container.
In the container is the media, and from the media grows plants. The main parts of that process are the container, the media, and the plumbing.
We’ve covered media types: now let’s talk about containers and plumbing.
Your options when it comes to container are very diverse, as you can use almost anything on hand.
There are all kinds of barrel systems, tanks, troughs, ZipGrow towers, etc.
For bed systems, a great option is for you to make your own grow beds with boards and liners. Liners can be fishpond liners or vinyl liners (like from old signs).
Not All Vinyl is Created Equal…
A note is that soft vinyl can leach chemicals that are toxic to fish. Rigid vinyl is safe, but research soft vinyl if you are going to use it. (Locally sourced vinyl is usually better than overseas-manufactured vinyl.) Often it ends up being easier or cheaper to just buy a pond line.
The great thing about self-built tanks is that you can size them to any space. Instead of fitting your space to a store-bought tank, you can size your tank to your space.
There are certain products, like Bato Buckets (Dutch Buckets) and ZipGrows, that adapt to a wide variety of space shapes and sizes.
>>> Remember: when you’re designing a system, think about how you’ll scale!
You always want to make sure that you have good drainage, too. Standing water is rarely a good thing.
The setup can be incredibly simple. It could just be a container over a tank. A standard IBC is a good example of this simple design: you chop the top of an IBC, use the bottom as a fish tank, and the top as the grow bed, and the grow bed drains right into the tank.
Aquaponics System Layouts
Types of Aquaponics System Plumbing
Flood and Drain (“Ebb and Flow”)
Regardless of orientation, you pump water in and you drain water out.
One most popular way to accomplish these is to use “flood and drain” (also “ebb and flow”).
In this method, you pump water from a sump into growing containers. The water rises up to a set point, and then drains to almost a very low level.
This method is popular because the root zone stays aerobic, while keeping microbes moist- essentially you keep the environment inside the bed aquatic and aerated at the same time.
A drawback is that every time the be is drained, the sump level fluctuates wildly. This means that you need a sump tank that can accommodate the volume of your tanks.
The alternative is constant flow. So in our tower systems, we constantly pump water into the tops of the towers, it percolates down through the towers, and drains back to our sump.
When I first started, I pumped water into the towers, which hung right above my fish tank, and they drained right into my fish tank. Oxygen levels stay high (because it’s aerobic) and everything stays moist.
In a gravel bed, there’s much more fouling because nothing disrupts the accumulation of organic matter.
What we’ve found is that if irrigation is correct and design is solid, you shouldn’t have too many problems using constant flow and constant drain.
There is a way to design halfway between the two; a lot of people do flood and drain but limit the rate at which the water can leave the container.
To do this you use a timer and an over-sized pump with constant flow. A lot of water is pumped into the container in about 5 minutes- more than the drain can keep up with, and it rises all the way up to the backup drain (Think of the hole in the side of your bathroom sink- same idea, and both are crucial if you want to avoid overflowing your container!).
After the irrigation time is up, the timer turns off and the container drains back down to the first drain. (Some people like to use a bell siphon instead of a timer, but I hate bell siphons.) The drawback to timers is that you need to use a submersible pump. Inline pumps with hard stops and hard starts do not like to be started and stopped a lot, so they’ll fail with a timer.
Almost all of these have to be a sump-based system, or else you need a very large fish tank that you’re pumping out of. Grow beds are best in sump based systems so that you can put them at any level. Whenever you’re working with an actual container and not something like ZipGrow Towers, you want it to be at a level that is accessible and that you can work with. The sump usually has to be a large volume in case all your beds drain at once. (It need to be able to accommodate the entire volume of all your beds together.)
What Crops Can I Grow in a Media-Based System?
Media based systems are suitable for a lot of crops, but that doesn’t mean that they are profitable. Like I mentioned in the Fundamentals of System Design episodes, you can’t confuse biological viability with economic viability!
Economic differences is the biggie here!
Large statured crops like tomatoes need a lot of support and interaction, which means that they are good in media based systems, but not raft systems. (Rafts are limited to short-statured crops.)
Root crops and fruiting crops also grow best in media systems.
Fruiting crops are suited to media based systems because they require more nutrition than purely vegetative crops.
Because media acts as a filter, it’s able to accumulate more nutrients than just water. Having high nutrient levels is the only way that these types of crops will grow.
Plumbing for Aquaponics Systems (and Drainage)
First up is the bell siphon.
Bell siphons are siphons that capitalize on the differences in hydraulic pressure to move water.
The nice thing about these is that you can go over the water level to drain a tank into another container. It’s like an SLO with a cap on it- so when the water starts moving up and draining through that inner pipe, there’s no opening at the top of the outer pipe to release pressure. (That’s where the word “siphon” comes in.”)
This means that if the inner pipe extends below the bed, i the entire bed will drain. What stops this from happening is a rubber tube that extends to the minimal water level. When the water reaches the minimal water level, air enters the siphon, gives a release in pressure, and fills up the bell.
Once the bell is filled up, the water level in the tank can rise again. (This is a very old technique used widely in toilets a few decades ago.)
Timer Irrigation & Drainage
Last of all is floats (floating outlets): A flout is an outlet plumbed to a “little boat” which floats on top of the water level.
As the water level rises, it reaches a point where the outlet cannot bend up that high. When it reaches that point, the water fills up the boat, and the boat sinks. When the boat sinks, the siphon starts. The water level drops, and the boat is floatable again.
This process repeats itself over and over so the water level is constantly rising and falling.
A Note on Bio-filtration:
Bio-filtration is using something to host the bacteria that break down chemical compounds into available resources.
Two important measurements for bio-filtration are going to be BSA (Biological Surface Area) and SSA (Specific Surface Area).
The nice thing about media is that it has a large amount of Biological Surface Area, which is the total square footage that your microbes have to live on. This could be particles in the water, the sides of your tanks, etc., but most of your BSA is on the media in your system.
Specific Surface Area is different, but still crucial to designing a good system. See our Youtube video on this for more details.
What is Specific Surface Area?
Basically, Specific Surface Area is a measurement square feet of surface area per cubic foot. So you’re looking at a measurement of area in an amount of volume.
An example is sand, which has a a very high SSA. SSA is also very high with fiber, which is why we use one.
Both SSA and BSA are important to Bio-Filtration.
We’ve experimented a lot and tried all types of systems and all types of irrigation and drainage. In our experience we’ve observed the benefits of media systems and constant flow over raft or ebb and flow.
Now all we use is ZipGrows– after you use them, you won’t go back to other systems.
Stay Tuned for More Aquaponics Info!
Let us know what you think!