The Good Aquaponics System – Part III

Aquaponics August 5th, 2009

I’ve been overseas for the last 2 months, and the system has been under the custodian ship of the lovely Eleanor. She did remarkably well – the professional system is still going strong with zero losses. Unfortunately Ele turned the power off to the old system and forgot to turn it back on, killing all 50 fish. She was very upset. I wasn’t too worried, I seriously expected to return to zero fish, so I’m really happy to have 100.

The system is operating, but it was getting a little bit healthy. Nitrification is an acidic process, so the pH goes down, and you need something to buffer it. This is usually some sort of Carbonate. I had been using Potassium Bicarbonate, but obviously the buffering effect had worn off, because when I measured pH when I arrived home it was 6. And that’s as low as my test kit went, so who knows how low it actually was. Potassium Bicarbonate is quite expensive, so I went and bought 20kg of shell grit (commonly used for chooks), which is Calcium Carbonate (i.e. limestone, chalk, garden lime etc). I’ve put this in the beds and the pH today is 6.4. On with the photos:

The beds have filled out nicely

But the plants aren’t exactly healthy:

And some weeds have really taken ahold!

But I think this might be due to the low pH. pH has a big impact on uptake of nutrient. I’ve also dosed it with chelated iron (just incase).

Some of the fishes dorsal fins have gone white at the tips, so I’ve dosed with salt (it’s now at 4ppt) and I’m told that this is a sign of stress – could be pH again. Just as a side note, 4ppt in a tank of my size is actually 10kg of salt. That’s a bucketfull!

So they’re eating, and they’ve grown, and the plants are doing pretty well. The water temperature is between 6 and 10 degrees C, which is fantastic for trout. I haven’t had the growbeds freeze (I keep the water running the whole night) which means that the bacteria are still alive and doing their job. Things are looking good for an October harvest (touch wood).

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