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| The trial system configuration |
Goals
My goals for this system:- Keep it small, but large enough so that we can stabilize the system and keep it running for at least one whole season.
- Minimal investment in structure - let's not build a huge greenhouse before we know we can actually make this work.
- Use a nutrient solution transport scheme that has had high reported success and minimal impact on the fish.
- Make the framing components extremely easy and cheap to build (the picture above is not accurate to the final specs)
- Large plumbing for minimal cleaning.
- Keep the pump accessible.
- Design for maintenance.
- Design to mitigate failures and fish-death.
- Design for future expansion.
System Design - Overview
To achieve these goals, I have set out to do the following:
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| Plumbing View - Grow bed assembly removed for clarity |
- The system is a 200 gallon cone-bottom fish tank, a 100 gallon sump, and two 50 gallon grow-beds. This technically gives me a 1:2 ratio of fish tank to grow-bed space, where the preferred ratio is 1:1 or 2:1. I can compensate by simply not adding as many fish.
- By putting this on my back porch, I have an enclosed space that I can manage and is convenient for monitoring and upkeep. No structure builds required. The downside is that I need to supply auxiliary lighting, which means either buying or building lights.
- I toyed around with CHOP-1 and CHOP-2, and finally settled on CHOP-1. While I'm not convinced of the problems that detractors of CHOP-2 go on about, CHOP-1 plumbing is easier by far.
- The framing components for the grow-beds will be made of 2x4 lumber. All the cuts are straight (again, ignore the portions of the picture where this does not appear to be the case, that was an early draft). Assembly can take place with screws and carriage bolts, the latter for the most significant load-bearing members to add rigidity and strength.
- I will have to double-check the size of the NPT fitting on the bottom of the fish tank, but I believe it's 2". I plan to run the largest diameter reasonable from the fish tank to the grow-beds, to ensure good flow and minimal clogging.
- All the plumbing should be sufficiently accessible. Space is a bit cramped, but I have positioned the system components such that nothing is completely inaccessible.
- All plumbing will be valve-governed. The under-tank plumbing will probably be glued wherever slip fittings are used. This is to mitigate a pressure disaster. Not visible in the picture above is a valved outlet, which could be used to drain the majority of the system if things go very wrong. The valves will allow me to disassemble whatever portions of the system I like - within reason - without having to move the fish and drain the fish tank. Where pressure should not be a significant issue, I will probably use unglued slip joints, as is the common tendency (this allows easy cleaning of the smaller pipes, as they can be disassembled).
- I have tried to design the plumbing such that if there is a pump failure, the entire tank doesn't drain to the sump. The system is configured such that the water in the fish tank must rise sufficiently to spill over into the grow bed flood plumbing. The spillover tube is open at the top (the blue vertical tube in the illustration above), so that no siphon can form.
- Finally, with the size of the tank, grow beds and plumbing, it should be very easy to expand this system by adding upwards of 6 more grow beds, without changing out the tank. Additional sump will be required, if/when we get there.
Related Topics and Research
In doing my extended research, I investigated the keeping of koi. These fish have rather particular water clarity needs, and so I felt they would make a good study in just how clean one could keep a pond or tank, and in what methods would serve to best achieve this. Some of the interesting tidbits I collected from the koi pond building guides were:- Large plumbing is essential. Under-sizing leads to clogging, mainly due to the typically low flow rates.
- In koi ponds, once practice is to feed into swirl filters first, then get to media filters - if you're interested in removing the maximum amount of contaminants and not growing plants with them, that is. Multiple swirl filters can be attached in series.
- Bottom drains work best, as they encourage the capture of just about everything that falls to the bottom (thus my choice in a cone-bottom tank). These are usually built into the koi ponds during construction.
- Pipe purging can be done by creating a fast water flow. In some koi ponds, this is done by disabling the filter feed pipe, draining the swirl filter, then enabling the filter feed pipe. This (theoretically) allows water to flood in rapidly, dragging accumulated contaminates through the pipe and into the filter. I should be able to do the same with my valve system.
- Ideally, the pump should be places after the filtration assembly. This improves pump life and reduces clogging at the pump.
- Any inline heaters, UV lights, anaerobic filtration equipment, water polishing, and such, tend to go after the filters, and either before or after the pump.
While some of these points will not be highly applicable to aquaponics, I think some practices may prove beneficial. In a future iteration I would like to employ some swirl filters to clean the water in prep for delivery to a NFT or DWC array.
Lighting
One of the unfortunate side-effects of using the porch is the lack of direct sunlight. There is plenty of diffuse lighting, but I do not believe that will be sufficient for even my trial plants. I have been investigating various lighting options. Here's what I've considered:
- HIDs - low entry cost but high energy usage and possibly short lifespan of bulbs.
- Metal Halide - bluish light that is good for vigorous plant growth.
- High Pressure Sodium - reddish light that is good for fruiting.
- It is ideal to use both kinds for the different stages of plant growth, but this requires a ballast that can energize both kinds of bulbs (or more than one ballast).
- T5 fluorescents - moderate investment, lower energy usage than HIDs.
- Bulbs reportedly need to be replaced after 6 months.
- LED - higher initial cost, lowest energy usage.
- Research is comparatively scanty on LEDs for plants, but there is a growing industry and community.
- DIY LED lights are possible.
My ideal lighting solution will probably be LED, and by that I plan to manufacture my own grow-lights. There are several how-tos and at least one excellently engineered build-guide. WHen compared to the buy-and-install of HIDs and fluorescents, LED lighting construction is not trivial.
- Power Supply
- An LED driver is required. You can get LED drivers and drive them with D/C power, or purchase an all-in-one driver unit.
- LED Assembly
- Some people use red/blue diodes, others use white.
- Power LED lights require heat dissipation measures - a heat-sink or metal backing plate.
- Cooling
- Passive cooling is obvious and easy.
- Active cooling requires power; the LED power source might provide for this, otherwise separate power requirements must be met.
Aeration
To assist with aeration, I plan on eventually having two systems in place:
- Venturi aerator - this will be driven off the return water feed, so pump-powered and run directly back into the fish tank.
- Air-stone pump - ideally with a backup power supply, this could run air in both the fish tank and the sump.
There are several online examples of DIY venturi aerators. The construction is extremely simple, so I will be experimenting with that as well.
Project Road Map
I will be performing the testing and evaluation step first. All other steps will occur as time and materials become available, so the order of events will not necessarily be as listed.
- Build, test, and evaluate critical system components:
- Siphon construction
- Venturi aerator construction
- LED lighting
- Install the electrical
- Build the grow-bed support frame
- Acquire:
- Fish tank
- Grow beds
- Sump
- Miscellaneous system components
- Plumb the system
- Build the full lighting fixtures
- Grow Bed assemblies
- Build, install, and test the siphons
- Evaluate fill/drain times against estimates
- Cycle the system
- Acquire fish
- Add plants
- Grow!
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