Aquaponics System Design Philosophy (Part 1)
This episode will cover:
This episode will cover the fundamental principles of system design. Dr. Storey focused these principles on the needs of the system and how those needs can be fulfilled while supporting system resilience, ease of management, and system response.
System design is preceded by three steps:
- Identify the purpose of the system.
Will you be growing vegetables? Raising fish? Are you growing for fun, family, or for a specific market? outline your goals and have a solid purpose in mind.
- Acknowledge the needs of the system
- Decide on technical solutions to meet needs
The goal is innovation, not invention.
Instead of using the plans of someone else, use the guidelines and tailor it to your needs. Your unique circumstances, needs, and desires should dictate how you plan. Now, there are a lot of great designs out there done by very competent poeple. They’ve come up with incredible tools and techniques. By all means, make use of that community. Be open minded, but take things with a grain of salt. Pay attention to who’s talking. You are going to use that information once the need is recognized, to figure out how to fulfill it.
Say you are building a system to grow out trout for market. You’ll need high quality water and probably will need a simplified single pump or a double pump system. Temperatures will need to be low. Your focus will be fish-centric rather than plant-centric. Essentially, your system will be designed to keep the fish alive. If your goal is to grow a lot of produce, on the other hand, you’ll choose a different kind of fish, and you’ll be able to have poorer water quality.
Dr. Storey’s Design Recommendations
Dr. Storey prefers single-pump systems, but note that you will invest in more equipment to provide fail safes. He also likes to split the flow. (This means that water returns from both fish and plants, gets pumped up by one pump, then is sent part back to plant and part back to fish.) There are challenges to this; the water sent back to fish is low quality, which is fine for our species of fish, but not for all species. Another preference is operating all components under pressure (rather than using solely gravity). Pressure allows us to blow our lines out, time certain zones on and off, and more. These are more difficult under gravity flow.
A fourth preference is low stocking density. Some people think that low density isn’t worth the effort. In some markets, fish have low value, and it’s not profitable to do fish at all. (Now there is a big question here between hydro and aqua, but that is for a different podcast.)
The final recommendation is for high BSA. This makes all chemical processes much more quickly.
Lets break all of those things down and look at them in more detail…
A single pump systems allows you to minimize losses if there is a failure. A single pump setup also reduces the the chances of that failure happening. The reason for this is the idea that the more parts you have moving at any given time, the more likely you are to have a failure. When you have several pumps going at once, if one fails the whole system fails. In two pump systems, unless you have the right fail-safes, you could pump a lot of water out of your system, kill fish and plants, and have a big mess on your hands. With a one pump system, we can have a backup pump ready to go in if the other pump fails. We know immediately when our pump fails, and we have quick connect collars on our pumps which makes it easy and fast to put in the back up pump. Redundancy is important in any system- having a back up is always a good idea. You will never regret having extras.
Another reason to build with a single pump is that it lowers costs. It is not only more efficient in electricity use, but the initial cost is lower.
If you can’t dig a sump, then you are stuck with a two pump system. In this case, you need to have the right fail-safes. One useful fail-safe is to build your system to have float switches. These will give you the ability too turn your pumps on and off, keep them from running dry, etc. Also, have backup pumps for both of your pumps. You’ll have to buy four, but it will be worth it.
Split flow allows single pump systems. A con to split flow is that it limits you to fish that tolerate low water quality. However, split flow eliminates the gravity feed element, and it allows you to turn over a lot of water. One of the concerns that a lot of people have with split-flow systems is that the fish waste is just circulated around and a round, but this just isn’t true. Although the water quality isn’t pristine, you can filter 75% of system water once per hour. The resulting water quality is perfectly sufficient for breeds like Tilapia.
Under Pressure Irrigation.
Pipes clog. And they clog more easily with low pressure systems. High pressure helps avoid clogging and allows you to blow them out when they do get clogged. Pressurized lines gives you more flexibility with how you deal with problems in the system. Obviously gravity flow is practical for at least one part of your system: drainage. You will need gravity when irrigating water from towers back to the system. (There’s no benefit to using pressure in your drainage, which is a really simple part of your system.) It’s feeding the system that requires pressure.
Low Stocking Densities.
We use low stocking density because we have unique circumstances here; we can’t sell live fish because of some grey legal area (causes largely because of invasive species concerns). Fish here isn’t worth much and consumers aren’t that sophisticated with how they deal with fish. There’s a lot of imported fish. Altogether these factors keep fish from being a valuable product here- it’s not worth it for us to sell them. We have 600-700 Lbs fish in our system right now- this is a little higher than usual for us (fish fry, anyone?) I recommend 1 LB per 8 Gal to 1 LB per 10 Gal on the low end.
IF you are in a place where you can sell live fish and get around compliance issues, and if fish have a high market value, then fish would probably be worth raising, and the purpose of your system will shift more towards fish. If this is the case, you can go with a higher stocking density. But for us, our plants are worth much more than our fish are. (We could sell tilapia at $2 per LB and sell them once a year, whereas we can sell our greens at $4-6 per LB and grow eight crops in a year.) The payout just isn’t worth the bother. Instead, our fish are our pets. They’re colorful and some of them are 8 or 9 years old. We’re okay with that because we make more on our plants. That’s why we advocate low stocking densities.
This is a no-brainer. No one will tell you to have low BSA. (If they do, run away.) The microbes are the heart and soul of the system. The more microbes, the happier your organisms, the faster mineralization and nitrification take place, the more response you will get, and the more immediate your responses will be. Our extreme BSA allows us to feed aggressively and see a quick response in ammonia levels and nitrate readings. (Over the course of a few hours, we can run up thirty or forty points.) Now, there are always going to be problems, but the more responsive your system is, the easier it is to manage, and more potential it has in regards to production.
Those are the main design recommendations from Dr. Storey. He did not invent any of these principles, but rather adopted and reframed them to fit our setting.
Use a single pump, split flow, operate under pressure, use low stocking densities, and have high BSA.
This will support resilience, responsiveness, and management flexibility.
Tune into to the next episode, which is the second part of this episode.
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