Right. Now for something completely different. How to turn a small IBC aquaponic (AP) system into an oyster display tank. You can’t be serious? Well I am, so here goes.
Some time back I showed you how to build a small home AP system using an IBC. This week we decided to design and build an oyster display tank to stock these succulent molluscs in our restaurant, the world-famous Old Gaol Restaurant at the museum complex in Knysna, South Africa, for the annual Knysna Oyster Festival.
Let’s start by listing the differences between the two systems.
- The AP system uses fresh water, the oyster tank, saltwater.
- The AP system has plants, the oyster tank has none.
- The AP system stocks fish, the oyster tank, mmm, oysters.
- The fish need food, the oysters don’t, as they are being purged.
But there are also many similarities.
- Both systems need to remove harmful Ammonia.
- Both systems thrive on elevated dissolved oxygen (DO) levels.
- Stocking densities for the volume of water is important.
- Both species have specific temperature requirements.
It made perfect sense to thus diversify somewhat, given the low temperatures that were causing such problems with the Tilapia. Oysters thrive on temperatures in the 8-16 deg range, exactly what will seriously compromise or even kill, Tilapia.
So, how did we go about it? Well firstly we netted the remaining fish and moved them to the big “Koi” pond to see how many will survive outdoors through the Winter. Then we emptied the growbed, replanting the vegetables in other growbeds and in soil. The tank and growbed then had to be thoroughly washed and sterilised. I use a chlorine and hot water mix to sterilize tanks, as it kills any bacteria and other uglies, and gases off after a few hours if left in the sun.
I used the existing submersible pump, but added a venturi pipe to suck in some air and provide some great aeration in the form of fine bubbles from the spraybars.
The flood and drain cycle of the AP system would work just fine for an experimental “tidal” system that I had been planning for some time. Here is what the tank looked like after rigging up.
What you see at the bottom of the old growbed is coral, which I am hoping will provide some bio-filtration. The oysters are going to be placed on top of this coral and I estimate that I will be able to stock 100-200 medium oysters for the given volume of water (about 300L).
The way the system works (which I am hoping will fool the oyster into thinking it is back in it’s natural environment) is that it will flood the container up to the standpipe for about a half an hour, all the time bubbling fine sprays of air into the water. Then the pump will go off and it will drain and then lie dry for 15 minutes. Then the procedure will be repeated. High tide, low tide, high tide, low tide.
Here is a shot of the spraybars in action. Note the fine bubbles.
The drain into the container also adds more oxygen by the waterfall effect of the falling water.
The venturi was just achieved by placing a t-piece into the suction line and letting it suck some air from above the surface. This took some tweaking, but it seems to work just fine now. Here is what it looks like.
We have now placed 6 medium oysters in the system as “crash test dummies” and will monitor their condition until the Child Bride and I stock the system next Thursday. I’ll keep you posted.