PLJ's Big Concrete Tank System

PLJ

I mentioned in my introduction thread that I have a large concrete rainwater tank.
The tank holds 90,000litres but I plan to keep it down around the 50,000-70,000litres mark.
I plan to raise rainbow trout (Oncorhynchus mykiss) to a reasonable harvest size over the cooler months of the year. The large volume of the tank may mean that I can extend the 'cool' season somewhat but, since it is above ground, I imagine that some of the volume advantage will be lost. Besides, like many others on this forum before me, I want to try my hand at barramundi (Lates calcarifer) during the warmer months so the rainbows will need to move on by late November or so.
This is what it looks like:

Charlie

She's a bewdy PJL, thats for sure :thumbright:

It will be cool to watch this develope, you got any idea's yet how you might incorporate AP?

PLJ

Charlie, some form of DWC such as bamboo rafts will be my limit initially, I think. I am open to suggestion but, with such a large volume of water, I can't visualise how I can effectively incorporate sufficient grow beds for filtration without going overboard - I can only eat so many vegies! I have had thoughts along the lines of a recirculating fertigation system for large ornamental plants in containers.

PLJ

Here is another view of the tank after it was cleaned out, partly filled with bore water and covered with cheap bird netting. I had to sew together sections of the netting to make it wide enough. I used fishing line, which I hope will last at least as long as the netting itself, but time will tell.

Charlie

Yea the options are endless, but as you say... coming up with something practical for your family will need to be the goal.

Im no aquaculture expert but because you have such a large body of water it would be a shame not to get a good stock volume in it. Perhaps primarily some aquaculture type filtration could be incorporated for the bulk of removal (like sand filters or bioball drums)... which would have a mall footprint.

I could even vision a walkway around the tank for ease of fishing etc..

Then you could just run a DWC and maybe a couple of beds as some secondary filtration for your vegies to feed the family.

Just spit balling..

:thumbleft:

rsevs3

You could look at fruit trees. Something that is nutrient hungry. Mango maybe? :dontknow:

PLJ

Good one, rsevs3. Why go ornamental if there is a possible edible output? Using fruit trees is a great idea, especially since many varieties have been developed to grow in containers. Passionfruit (Passiflora edulis) is a gross feeder that immediately springs to mind, although not actually a tree.
I am also keen to see how large bamboo plants perform with fish-waste rich water circulating past their roots.

rsevs3

I have read that passionfruit has a very aggressive root system and you will need to consider it when designing your container. What i mean by that is, make sure you can easily clear the roots out of your inlet/drain.

PLJ

I introduced 100 rainbow trout fingerlings and 33 silver perch (Bidyanus bidyanus) fingerlings into the tank in late April. The status of the hapless silver perch is unknown, or perhaps MIA.
Since then I have worked hard to get my head around biological filter theory and then to put it into practice.
The following pics document my progress:

PLJ

I decided to position the filter drums at the same height as the surface level in the tank so that there was no chance of the tank emptying if the return pump failed This way if the pump fails then the tank and filter drums just find their own level.

PLJ

I have joined two 205litre drums using uniseals and a short length 3" PVC. The uniseals seem to work perfectly and, even at inflated Perth prices, are a much cheaper proposition than using tank outlets.
When I made an initial inquiry re uniseals, the importing agent in Queensland told me I wouldn't be able to join two drums this way due to lack of access to apply force on the pipe to get it through the second seal. Well, I am left to assume that I am stronger than he is!

PLJ

I couldn't get as many uniseals as I needed to set up my filter system the way I intended so currently just have the biofilter itself and an adjacent 'sump' drum. This drum receives the filtered water and houses the pump, which is just a Weipro 3900LPH unit. I plan to use this pump for my IBC system when I eventually build it but, it in the meantime, it actually has much more capacity than my fledgling filter can handle. Gravity feed from the tank is great at bottom of tank level (2m head) but the flow reduces markedly as it flows upwards to the biofilter inlet.
When I can, I will introduce another drum for finer filtration, perhaps with charcoal and shell grit as the media.
The medium I chose for the biofilter, after much time and effort spent on getting quotes for bulk quantities of scouring pads, etc, consists of shadecloth and a similar black windbreak material that I have rolls of. Hopefully this combo will do the trick.

PLJ

Rather than just draining fish water for filtration directly from the tank at its bottom outlet, a mate of mine suggested that I retrofit some PVC pipes with plenty of holes in them to provide coverage across the expanse of the bottom of the tank. Then, with inflow water creating a slight vortex circulation, the solids on the bottom might find their way to the holes in the pipes and be drawn away. That was the theory and I thought it worth a try, although I admit to not being overly keen to the underwater work required in the tank.
I made a cross out of four lengths of 25mm PVC (with end caps) joined with a four-way joiner. This was connected to a short length of 40mm PVC to be shoved into the 50mm tank outlet from the inside. It would have to be assembled inside the tank, since it was an unwieldy 7m across.

PLJ

I needed assistance to fit the drain so I collared my kids when they came home from school. Too bad that the sky had gone black, the temperature had dropped markedly and rain was starting to fall! The fish needed filtration!
My son was up to the challenge and agreed to climb down into the tank and take responsibility for joining the pipe pieces as they were fed in to him.

DrLuke

Nice work. Wish I had room like u.

What was your intended plan for the second barrel that you had to make into a sump barrel.

With 3000l/h you might have to go 50mm pipe to the center of your cross + a 50mm t, then drop it to 40mm on the three other sides. 40mm leading to outlet will be a bottleneck.

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