Backyard Aquaponics
A place to discuss aquaponics

I agree the Tri-Nations was a small joke this year - none the less. I noticed on one of your blogs that your are installing a solids filter in the new commercial system (I see that in your first system you did the same) Do you feel it's neccesary for water quality? In theory the gravel is working as a massive filter and I can see the amount of waste that builds up in it - are you doing this as a precaution? Why I ask is that I am thinking about running a seperate pumping circuit from the lowest point of this pool through a gravity filter - just to remove the majority of solids - with the tight budget on this project I can't make up my mind if it should be done now or if it can wait for a little later.

Worms do a really really good job of disposing of the solids from the growbeds.

So, not much has happened since my last post, I started on the grow beds and immediately came across a lot of problems, the entire site is built on rock and BIG rocks at that. I originally wanted to dig down and cast a slab, including all plumbing but this is no longer feasible. Attached is a picture of the form that we have now put together to cast above the ground surface 12m x 2m (7m3 of fill needed).

This form took quite some time to get right as it is 100% level, thus preventing any problems when the grow bed is eventually filled. Very slow start but things should start speeding up shortly - now that I have worked out a method to cope with the site. Any comments would be appreciated; I may be able to do things in an easier manner.

The whole in the middle is for a 110mm drain pipe, the ground curves up at this point and we spent a good couple of hours chipping through shale to get to a decent depth - rock is not really noticeable from the pic but trust me it's there.

For that particular site, yes. My reasoning is that we are building 100 x strawberry towers together with 24 x 6m grow beds. What I have learnt (by bitter experience) is that strawberry towers do not like ANY solids and clog up really easy. I am also adding an additional inline filter to the strawberry line, just in case.

Also, we are looking at reasonably high stocking densities which equals pretty large quantities of uneaten food and poop. I'll show you the solids build-up at my other commercial site when you come for your visit.

As far as your build, two things. I hire metal formwork for my slabs. Very cheap to hire, easy to put together and gives a nice smooth, 100% level finish. I gave up on wood boxing in frustration.

Secondly, I haven't had much luck with press-in drain pipes that you appear to be using. If you are using a centre drain, the pressure exerted by thousands of litres of water compressed into a 80 or 100mm pipe is excessive and the joints blow out. I had to dig up my drains and replace the joints with PVC glue-in joiners and now they work fine.

Great work, keep it up.

Cheers

Thanks for the input, I was going to pour the slab tomorrow and was quite happily putting together the pipes with the press in joints, I will get hold of my plumbing supplier and get the glue in jobs. I reckon that I need to come down sooner rather than later as I am concerned with solid build up and I too am going to need to run high stocking densitys for this project. I'll see what flights etc are available during the course of today and give you a shout later.

Who do you hire from? Is there maybe a branch up here?

I hire from Knysna Equipment Hire. They don't have a branch up there but any good scaffold hire company will have formwork in 75mm, 100mm, 150mm etc thicknesses and 1m, 1.5m, 2m etc lengths that you just clip together. The attached image is 100mm thick 3m x3m slab made out of 8 x 1.5m forms clipped together. Fill it up flush with the top and then just drag a straight edge across. Neat and simple. About R25/day to hire ($0.54)

Thanks SNTM! Looks to be just what I will be needing... I will check locally.

The fun never stops on this project, sponsors have re-thought their original proposal and now want to build a larger system, not in terms of tank size (84000l) but in terms of grow beds. I need to know what is the maximum stocking capacity of this system, I will be able to run 90m3 of grow bed (if needed) obviously the system would run different cycles to each bed (9 in total) or the fish will be sitting on dry land. I'm dabbling in very murky waters here as the production needed off this unit is very close to commercial scale on both the vegetable and fish output.

90m3 of growbeds will have ~ 36kl of water at full cycle. So say 40kl to be on the safe side.

Lets say this leaves 40kl of water in the pool.

40kl of water will support around 1200kg of fish (3kg of fish per 100 litres water).

90kl of growbeds will support 4500kg of fish (10 x 1/2kg fish per 100 litres gravel).

You will be at an excellent water/growbed ratio, and the system will have no troubles with solids build up etc.

With a lot extra aeration you could push the fish density further.

Things are moving along, albeit slowly, on this project - the funding for the project should (please!!!) be approved by the end of January so that I can get going, attached is an overview of what I would like to do - not to scale so please don't shoot me. The gray areas are grow beds, the blue is a collection area for water and will contain floating rafts, the green and gray areas are grow beds that will be suspended over the pool to utilize 'wasted' space.

The water collection area will have a number of 110mm pipes installed that will gravity feed water back to the fish tank (old swimming pool) and will also contain a pump on one end that will push water into the bottom LHS of the tank thus creating current / swirl.

Total growbed area =59m3 - I must be mad.

FYI, there is more area for additional growbeds (up to 90m3) but this will only be added if we find that the production from this setup cannot cope (which I doubt), the requirment is 30 meal packs per day, after 6 months running in period this would include: 1 fish, half head of broccoli, 160g spinach (or chinese cabbage) and two tomatoes.

It has been a very long time since I posted anything on this thread (or on this forum for that matter), this project turned into a huge feat and I am only nearing completion now. After my initial posts I did a lot of research into tank designs as I felt that I would like this system to be a prototype for commercial size systems. In that kind of scenario faeces becomes a big factor and extracting them is tantamount to the whole project. I will post a number of pictures as I went along the build. I originally ordered a liner for the pool but then decided against it as it would require a lot of man hours to manually clean the pool on a daily basis (once high stocking ratios were reached). I then designed the pool with a centre island; the water will then be circulated around this island with the help of air pumps (geyser pumps?) as well as drain back from the growbeds. This would create centripetal force and cause the faeces to move to the middle of the pool (alongside the sides of the island. I then placed drains along this island the would then suck up the faeces into a vortex filter, then overflow into a second chamber for bio filtration and then flow into the ‘sump’. The pump then extracts this was water and distributes to the growbeds. .
I am experiencing problems on the growbeds as they are now 14 meters long – and the gravel is beginning to settle, this doesn’t allow the water to filter through the stones fast enough when the siphon kicks in (63mm siphon), the siphon drains at around 120 litres per minute and the water just doesn’t flow to the siphon side fast enough. I may have to dig up the gravel (10 cubic metres per bed) and install some perforated pipes at the bottom of the gravel to work as an equalizer.

Any way – here are a couple of images from the build.

Any way – here are a couple of images from the build.

we had to use a very liquid form of concrete to puor into this structure, we had some hair raising moments as the formwork started to bulge in certain areas...