Aquaponics - New grow bed

Scoria has always been the media I favored because its perfect for aquaponics. I'll be using road gravel.

Here's some I prepared earlier.

Pictured here, and using chicken feet for scale, is a  path in my back yard. It's the same stuff I'll be using in my new grow bed. It's sometimes called blue metal, and in this part of the world we mix it with tar, and make roads out of it.

Scoria is great in all kinds of ways, but it's hard on the hands, and because of it's sharp edged irregular shape, it's actually difficult to dig into.

My new grow bed is big enough that I don't need to worry about the extra surface area scoria would provide. I'll get around 2000 - 2500 litres of gravel to fill it, and I'll use the existing system as a pre-filter to seed the nitrifying bacteria.

In a former life, this new grow bed of mine was an abalone growing tank used in aquaculture. As soon as I can stop switching between plans, I'll bu using it to grow veggies.

Aquaponics -Oops!

A few days ago I got some strawberry runners and, having no home for them, decided to make a small grow bed that would hang into the fish tank. When the main grow bed was flooded the water level in the fish tank would be below the new pot. When the main grow bed drained, the fish tank water level would be full to the top so the new grow bed would be flooded. No real problems there, in fact I felt a bit clever.

 I filled the pot with blue metal (road gravel in this part of the world) collected from my back yard. The day after I did this my pH went from 7.6 to 6. Now, I was told to expect a pH drop at this stage of fish-less cycling, and with the new gravel going in I thought it was within expectations.

The problem with pH readings of  7.6 or 6 is that they are at each end of the scale and as such it impossible to tell if they are actually beyond those levels. More on water testing aquaponics systems later.

Yesterday I discovered a white powdery substance near where I collected my gravel. I had a better look at it and discovered the gravel was dissolving! It was near where my flashing battery tail light for my mountain bike had rusted out so the conclusion I choose to leap to is battery acid!

I spent the afternoon washing out the system a few times, and now the pH is sitting at 6.8.

I was just a few days away from adding my fish so I guess its a good lesson to learn at this stage.