DIY Backyard Greenhouse Aquaponics Project - Part 5

DIY Backyard Greenhouse Aquaponics Project – Part 5

This post is continued from Part 4. We continue on with the aquaponics build, with final bell siphon adjustments, system water cycling, winter operation, and costs.

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Bell siphon & leveling woes

Then it was time to do the fine adjustments of the bell siphon.Bell siphon

I wanted to make sure that the siphon was starting and stopping correctly. Often this comes down to adjusting the pump flow rate.

So I starting pumping water into the growbeds, and while waiting for the siphon to start was surprised to see water spilling over the back edge!

Shutting off the pump, I pulled the standpipe out and let the water go back in to the fish tank.

I rechecked level on the growbeds and it was off by over an inch in 4 feet.

Looks like the ground is softer in some places than others!

So I re-packed the ground under the concrete pavers, and re-leveled the growbeds.

Two tools that were helpful in adjusting and repacking the dirt: a simple rubber mallet, and my Japanese Ika hoe from The Tool Merchants.  The hoe loosened and moved the packed dirt, and is small enough to get around posts and under the beds.

I used the mallet to pack the dirt, then tamped on top of the paver to ensure a level surface.

System (water) cycling

System startup, or cycling, is the process of building up your ammonia- and ammonium-eating bacteria to allow a healthy ecosystem for fish and plants.

The conversion from ammonia to nitrite to nitrate is called nitrification.

How long this takes depends on water condition and temperature, and can be done in several ways. Using goldfish to do this is quite common.

I used the larger size “feeder” goldfish from the pet store. Goldfish (which are carp) are quite cold hardy, tolerant of poor conditions and inexpensive.

I also took some gravel and filter media from our indoor fish tank and placed it in the growbeds. This will help colonize the growbeds faster with the necessary bacteria.

It turns out I was too hasty when adding my fish. This was partly because the water was too cold and I didn’t have the water pump cycling all the time. And as a result I lost most of the fish.

So I decided to do fishless cycling instead. This involves adding a certain amount of pure ammonia to the water to attract and grow the necessary bacteria.

The advantage is that you can push the ammonia higher than is possible with live fish. This means it’s possible to cycle faster with less stress (on you and the fish).

It’s super important to only use 100% pure ammonia with nothing else. The stuff from the dollar store won’t cut it. It has fragrance and surfactants even though it says 100% ammonia.

I found mine at Ace Hardware, the store brand called janitorial grade ammonia. It was less than $3, and will do many tank startups.

Please see Backyard Aquaponics Basics for more info on the nitrification process. Also see this and this and this for more info on the fishless cycling method.

Filters, sump & other accessories

Like most aquaponics setups, there is no fish tank “pad” filter. The pump moves fish water directly into the media growbeds.

I will add red wiggler worms to the growbeds to help take care of the solids. I may need to to add a swirl filter or sump to separate out the solids first.

Another planned improvement is a venturi aerator fixture to the pump supply line that Tees off and returns back to the fish tank. See Rob Bob’s video on DIY venturi aerators if you’re interested.

Update: This addition is now done! See the venturi aerator page for more info.

Winter operation

We have seen -24°F winter temperatures in the last 15 years. Though our average temperature puts us into USDA zone 6, I wanted to be prepared for the real possibility of very cold weather.

So I was concerned about winter operation of the AP system, and I didn’t want the pipes freezing and cracking or ice forming in the grow beds or drain lines.

DIY Backyard Greenhouse Aquaponics ProjectI used non-fiberglass (because fiberglass doesn’t insulate when wetpipe insulation around all the exposed pipes to retain heat and reduce freezing potential. I think this is more important on pipe that doesn’t contain constantly flowing water, like the equalizer pipe between barrels.

This pipe always has water in it, even with the pump off and barrels drained, so it’s more prone to freezing. I’m not sure it’s strictly necessary (yet) for winter operation, but it’s cheap insurance.

Another feature I will likely be putting in is a constant slow drain from the equalizer back into the fish tank. This will make filling the growbeds slightly slower, but allows the whole equalizer pipe to automatically drain when the pump is off (at night).

This should nearly eliminate the danger of frozen broken pipes. One issue may be the small pipe size or valve freezing before the equalizer is drained, but we must EXPERIMENT! Yay!

I’m also considering adding an external siphon to be able to drain the water all the way out of the equalizer pipe on every cycle. The thought here is that I can keep this water moving and from getting too cold, though it doesn’t guarantee the pipes won’t freeze.

Another AP site, owned by Jeremiah Robinson (an energy efficiency engineer by day), is all about winter aquaponics (sadly no longer maintained). It was where I found some good info about winter aquaponics operation in cold climates.

Jeremiah has many suggestions, among these are:

  • Don’t heat your greenhouse, because it’s too expensive
  • Insulate all pipes, growbeds and fish tanks
  • Air-seal fish tanks and growbeds with row covers (i.e. Agribon) and plastic – this air exchange is where heat is usually lost
  • Limit pumping during winter nights – about one cycle every 5 hours
  • Efficient water (not air) heating
  • Plant and fish selection for cold hardiness

According to Jeremiah, because winter operation of backyard aquaponics in cold climates is relatively new, not many people are experimenting and publishing their results.

I think he’s right. Other than the above site, I wasn’t able to find a great deal of info on backyard aquaponics in cold climates.

There are some forum discussions that talk about winter operation, but most of the information isn’t helpful, or are guesses about how to grow in cold climates.

But I will post my results, and let you guy know what I find out. Empirical knowledge for the win!

Solar heater

Also in the works is a solar water heater. This is almost free heating, without having to use electricity or liquid fuels.

Of course, it only warms during the day but with almost 500 gallons of water and a lid, it should hold heat for a long time.

Construction is easy: run a coil of PEX or copper line through a shallow box faced with glass or polycarbonate. Spray paint everything inside the box flat black (except glass), and tee off pump water through it. Adjust the valve until the water coming back is warm enough.

I will probably shut this off at night to avoid the danger of freezing. Preferably I would control the whole system with an Ardiuno or other programmable chip (Raspberry Pi, etc). But that will have to wait for another day.


Rob Bob’s bell siphon video

Zach Bauer’s off-grid aquaponics videos here & here & here

Aquaponics rules of thumb

Backyard Aquaponics forum

Pipe flow sizing chart


This project took a LOT of work, mostly in digging the hole.

If I had a friend nearby with a small backhoe or mini-excavator, it would have been well worth the cost of diesel. Much faster, and my back would not have protested so much.

It also took quite a bit of time waiting to afford components, which was the main source of the expanded timeline.

Speaking of components, here’s the costs:

2- 8ftx6ft cedar fence“Free”Salvage/reclamation
8 – 4ft 4×4 posts, approx“Free”Salvage/reclamation
14 – 2x4x8ft“Free”Salvage/reclamation
Steel braces & 2×4 hangers$30.00Big box store
Wood screws, misc length$10Existing supply
PVC pipe and fittings$200Best prices on most components from
Vinyl pump hose and fittings$60Local hardware store
Underlayment and liner$200ebay
Pond pump$10Friend’s yard sale
Insulation$100 Big box store

Was it worth the cost? Overall, I think so, but we will have to see what kind of production comes out of the AP system.

I’ve planted cold weather crops like peas, kale and arugula, and hope to start getting production soon.

I may want to add some LED grow lights to extend the day length. This will let me trick plants into growing better.

I estimated that it will cost $16 per month to run my large pond pump full-time. It is a little overkill for the size of the fish tank, and I don’t really need this big of a pump.

A smaller, more efficient pump would cost around $80, and about $4 per month to operate.

So the payback should be relatively fast, which I think is enough to justify buying it. Next month or so maybe.

I’m fairly happy with how it turned out. It cost about what I expected, but took much longer to complete than I thought it would.

I am looking forward to visiting the greenhouse on a cold snowy winter’s day and seeing the fish and green plants.

Possible future improvements

Sump tank – prevents large drops in fish tank water level. Could be used to remove solids before growbeds

Swirl filter – removes solids from fish tank water.

PVC towers or overhead horizontal pipe for lettuce and strawberries – vertical growing saves precious greenhouse space

Passive solar greenhouse upgrade – holds in heat longer and better, for more growth and less chance of broken pipes.



OK, that’s all folks! Do you have any questions or comments about aquaponics, sustainable homesteading, permaculture design or anything else? Ask your question down below and let’s talk! You can also use the contact form, or email me at info at thepermaculture dot life.

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