Aquaponics - Yabby farming

I'd really like to be able to grow yabbies for the plate, but they are a little too cannibalistic and need a lot of space.

After a lot of running stuff through the invention engine, I came up with an invention to save people who have fallen through ice.

But that's another story.

The stuff that came out on crustacean farming was a lot more interesting because I don't have the falling through ice thing to worry about where I live, and like eating yabbies.

I think I'll patent the ice thing after a little development.

In the mean time I think there's a way to grow a lot more yabbies in a lot less space.

In the past I mentioned a few ways this might be achievable based on some observations, and one was that if food came to the yabby, it would sit in it's hole all day and wait.

A yabby waiting in it's hole all day hardly ever eats another yabby also waiting in it's hole. The result is yabby utopia.

They would be free to move around if they felt like it, but wouldn't do quite so much of it.

Much more like cows in a rich pasture full of 20cm high green grass rather than a hen in a 30cm cube cage.

Or at least that's what I think.

So here's what you do...

You create a shallow tank that holds PVC tubes slightly longer than the crustacean and wide enough so that they feel safe and perhaps set at 45 degrees or vertical, or whatever it turns out yabbies like.

Not too wide. 12mm black poly pipe for new borns, 18mm black poly for when they are around 2cm-6cm, then thin PVC until maturity would be a guess. Actually thicker poly irrigation would probably cost less.

You set them in a gravel/scoria/clay ball media making sure there is a few feet thick of the stuff under the PVC tubes.

The more tubes you want to set per square area, the more depth of media you need. 500L of media can support around 12kg of life. (depending on how much you feed it)

Put something under the media or run a stack of PVC pipes with slots cut in them so you can collect water from all over the bottom.

Add a pump to collect water from the bottom. An air lift would be better because it's a zero head lift and they run at a tiny percentage of the cost of a water pump.

Next you add enough water so that your tubes are covered by only about 4cm of water, plus half the length of your crustaceans at the stage of life they happen to be. Adjust as required, but this can be pretty vague.

You fill the tank with duckweed and pump so it draws water from the bottom of the media and expels it above the media pointed in such a direction as to set up a gentle movement all through the tank.

A round tank would probably be best, but square would work.

Add yabbies.

The yabbies sit in their holes.

The duckweed's 3-4cm roots float past.

The yabby grabs one, pulls it down and eats it.

The yabby grows. And excretes stuff that is either ammonia, or becomes ammonia.

I eat the yabby.

Duckweed can eat ammonia directly which is probably why it can choke rivers and lakes so brilliantly.

Duckweed has crazy mad Fu.

Most plants require bacteria to turn the ammonia into nitrites, then another bacteria to turn the nitrites into nitrates which the plants then consume.

When a plant can eat ammonia, it will always get first crack at the available nutrient. It also floats so it causes a blanket of shade at all the plants that live underwater. So duckweed gets the double advantage of all the sunlight, and all the nutrient.

The tank would definitely need a glass lid because yabbies love to escape, and a glasshouse would make both the yabbies and the duckweed grow well.

You would need to supplement the nutrient by adding duckweed from another source if you had a lot of yabbies, or adding some peas or brussels sprouts or something. Yabbies eat everything.


That's it.

I'm pretty sure it will work.


  1. This is really good thinking, might it be possible to use ceramic instead of PVC or why not just use tin cans and recycled stuff.
    Crawfish is what the Cajuns call yabbies BTW.

  2. Ceramic would be extra good because it would add to the surface for the nitrifying bacteria to colonise, but in any system like an aquaponics system where you are holding the water pretty much for ever, you need to avoid metals. They have a habit of leaching into the system and finding their way into the foodchain. If you were dumping water it wouldnt be so bad, but in a closed system people lose fish to heavy metals. I'm not sure what a modern tin can is made of, but I'm pretty sure they are plastic lined these days, so I doubt anyone really cares what they are made of. But being a potter for 30 odd years means the ceramic idea is definitely worth pursuing.


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