Aquaponics - Karmic debt

My karmic credit must have been good over the last 24 hours.

Two potential system disasters averted by a stack of luck, and a few minutes.

The first was yesterday, and involved my NFT tubes being fed too much water, and getting too heavy at one end. The flimsy stand they are now on was even more flimsy yesterday, and it gave way. The result was 3 horizontal grow tubes all standing on end, in a desperate attempt to mimic their strawberry tower cousins on the other side of the grow house. The pump was delivering between 50 and 70 litres per hour and was, of course, carrying on as if everything was fine. Lucky for me, I happened to be out there and quickly made myself into a table and called for help to turn off the pump.

A close call.

This morning I went outside and found water all over the floor and a steady flow from the strawberry towers to the ground.

That's often a bad sign in aquaponics, but it was still flowing, a flow is a good thing in aquaponics.

Flow is a better sign than flood is bad.

Which is nice.

The water was flowing freely out of the lowest strawberry hole on the first strawberry tower.

The culprit turned out to be two small pieces of scoria that had found a way to block the exit hole.

I saw them in there the day before, but for some reason didn't do anything about them.

I've since removed them.

The fish tank got very low.

Low enough so that a fin was out of the water on my biggest fish.

But not quite low enough for the pump to start sucking air. I still had half an inch of water before that happened.

Given it was only the water from one strawberry tower, I figure I had about 15 minutes spare before the pump would have been damaged, and the fish would have been walking.

We all know fish hate walking.

This is what's known on the forums as an HSM!*

I was very, very lucky.


Still there was the problem of water. Refilling the system from the tap would have been just as bad for the fish as not having water at all. They would all die from temperature, pH, and chlorine shock.

But I managed to scrounge some water from within the system.

I turned off the strawberry towers, and the NFT tubes. I run the NFT tubes half full of water so there was around 10 to 15 litres there. I also took the stand pipe out of my grow bed and let that drain completely. That gained me another 30 litres or so because I run a shortened siphon so that the bottom 3/4s of the bed is in constant flood. I also had the water from the duckweed tank. That is what saved the day, because although now nearly empty, it had been topping up the fish tank water until the end of the hose found air and the siphon broke. But I drained what was left of that and added that to the fish tank as well. That got me an extra 20 litres or so. I also added 5 litres of water from a plastic tub I filled a few days ago. So most of the water was already system water, so the fish shouldn't have any problems with it.

My final recovered level looked like this.

Which was a pretty good result and would allow me to turn the system back on.


Way too close for comfort.


This is what the water looked like.

Not so nice

But I soon noticed some fish.

And then this.

Total time between these three photos was...

37 minutes and 19 seconds as checked by their time stamps.

I thought I was in for days of trouble followed by sick fish.

Everyone seems happy and (I think) all is well.

I need a solution for this kind of thing, and it was crazy of me to not have a second exit flow from each strawberry tower.

So close.

*Holy Ship Moment


  1. Start walking old ladies across the street for the next few months to build up your karma again!

    I've taken to adding multiple drain paths on my systems and building oversized meshed gates for all drains.

    My first thought was to raise the pump so it can only pump down so far. But you pointed out that will burn up the pump. So, my next thought would be to add a float switch to the pump so when the water level gets so low, it shuts off. Now I need to make or buy one of these. I like the idea of making one...

  2. Since I've been hanging out in electronics stores, I've discovered things like float switches are easy to come by. I'd like to make one, but I have a feeling I'd sleep better with a bought one :)


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