Dan's Pond

I built my 20 000L koi pond in March 2009.
Its roughly 3.5x7x1.2m
I have just under 40 koi, 4x 40cm, 8x20cm and the rest 10cm.

Heres what we did.

First we dug out the hole. (jackhammers were needed for a day)
Made the edges all level where the wall would be built and then all sloping down towards the drain.
Laid the plastic sheeting.
Used a drain from happykoi 110mm and plumbed that in.
Made a box for the concrete out of old wood around the pond.
Laid steel y-bar and wired it together
Laid steel mesh and wired it to the y-bar
Got strong concrete ready mix with 9mm stone poured in and spread and compacted so that it was 100mm thick.
Then I got a contractor in to build me the wall-double layer with no cavity using brick force every second layer and also having sideways interlocking layers in between. The front outward facing wall was done in face brick and the others in clay ROK.
I added two 40mm return pipes 300mm from the waters surface, an air hose and a top up pipe at the bottom as well as a pool light.
Had the sides and bottom plastered with full strength plaster and a larger cove made where the wall meets the bottom.
Let it dry out wetting it occasionally to slow the drying.
Finished the places where the pipes come through the plaster nicely and neatly and fixed any imperfections in the plastering.
Lighly sanded the plaster and cleaned out all the sand.
Gave three coats of super laykold waiting for it to dry a week between each coat.
Topped off the wall with tiles to match the rest of the house.

Now because the pond is so close to the house and the bedrooms are upstairs directly over the pond, we wanted zero noise. So no waterfalls, no splashing, no venturi and the filters are far away.
We also didn't want a lot of surface disturbance as we wanted to always be able to see the fish clearly and undistorted.

So there is a large dick type airstone under the entrance bridge driven by a Boyu compressor.
The water outlets are angled so that there is a anti-clockwise current in the pond and no still spots.

All the filtration takes place 25m away at the edge of the property.
There is a 2x1x1.5m settlement chamber with a heavily sloped bottom. Water comes in at the bottom of the deep end and is sucked up by the pump at the shallow end. There is also a removable standpipe in the deep end to flush the chamber.
Theres also a small chamber with a float valve for auto top up.


building...




inspecting...




more building...




almost there...




and done




crystal clear water




and a full pond pic




filtration

more images...









tiles look a bit grimy, thats from being oiled, it goes away with time.


Filtration:
110mm bottom drain
Settlement chamber(+-1000L)
Auto-topup
Pump: speck 750W
2x 3bag koi pond sandfilter (koi pond type gravel)
2x Ultrazap 25L (bio balls and some sponges inside)
15w compact UV tube.
2x 40mm returns

Gerald's (garder) maintainance schedule:
Daily leaf skimming with the net (theres hardly anything)
Daily sweeping anything on the bottom into the dain (again hardly anything)
Weekly backwashing and rinsing of the filter
Weekly draining of the settlement chamber (5% water change)
Weekly cleaning of the pump
Every 3 months removal of the filter gravel and washing it in a huge basin with pond water only
Every 3 months removal of the filter material in the ultarzap and washing it in a huge basin with pond water only



The pond took just over two months to build, attached is my costs spreadsheet, excluding my gardeners wages. He was the main digger, painter etc and me and my dad helped when we had time.

 

Look interesting Dan. Couple of things I may have done differently as the contractor, but if it's been running for almost a year with not cracks or faults, then maybe you got away with it.

I'm sure Henk will post a few tips/idea here... he has a lekker big Koi pond too!

 

looks great , im suprised that it costs that much to construct a pond

 

R35 797.85

The construction seems a bit 'unstable' if i can use that word. But like Zoom said "then maybe you got away with it"

 

No cracks, leaks, nothing, I had no experience with building so I just read books and forums and went from there. One thing I discovered a bit late is its a good idea to lay the first layer of bricks into the floor while still wet so its embedded in the bottom. Was thinking about using concrum or something in the cement for waterproofing but I spoke with an engineer from Lafarge that specializes in cement and he said it wouldn't be necessary.

I would have loved to have made it deeper and more of a slope on the bottom but it just wasn't possible with the solid rock beneath.

I was also thinking of going the hand packed concrete way, the way our swimming pool was made, but i wasn't brave enough to attempt that.

I'd be really keen to hear what you as a contractor would have done differently.

Don't have any leaks or cracks so I'm very happy, but would love to learn what could have been done better.

lol, its like a swimming pool. only more expensive filters

base/walls/waterproofing?

I was thinking its solid. :amazed:

 

some more build pics:





guys, tell me what I did wrong or could have done different.

 

Hi Dan,

There is really nothing fundimentally wrong with the way you did it... but from my experience of building pools, I would have done something different. Your koi pond is pretty much the same size as a small pool, so I would have basically followed the same steps.

The only thing that really concerns me is the fact that at the bottom, you have a brick placed onto concrete, which creates a joint... or a potential crack area. You are relying on the plaster to prevent the crack from happening there.

What I would have done is case foundations approx 400-600mm deeper than the pond floor (approx 500mm wide). Then bricked up to the height required. After the wall is built, fill the inside of the pond to the height required, and compact to 95% ModAsh (Which is a technical term for VERY HARD!) using a whacker. THereafter using Y10 or Y12 Rebars to reinforce the bottom, as well as up the sides, as well as the mesh.

From what I gather, you've seen a pool being built the method, so you understand the handpacking of the concrete method. This then creates a concrete shell. What you have done is created a plaster shell... and relying on the fact that you are not going to have any movement between the brickwork and the floor concrete. The way the pool guys do it is that even if you have a bit of movement with the bricks, your concrete shell is solid and won't move at all.

I think the reason you have gotten away with it this way is because on the other size of the wall you have garden and house pushing against the force of the water... so your brickwork won't shift (theoretically). So you should be safe.

If you ever do it again... go ahead with the handpacking route... it's not that difficult, and when you order the concrete from La Farge, you actually ask for what they call Pool Mix... which is a 30mPa mixture, and comes fairly dry... so it's easy to pack by hand.

Just out of curiousity... what strength concrete did you get delivered there? Are you sure it was a 9mm stone, or a 19mm? (Reason I ask is because usually 9mm is a lot weaker).

Needless to say... what you have done looks stunning... and I'm impressed.

 

im learning a lot on this thread

 

I hear what you saying with the foundation. The problem i had was the whole bottom was solid bed rock, like jackhammers couldn't do anymore damage to it. I would have needed a mechanical digger and tnt to get any deeper. So my plan was to rely on backfilling the wall and that I was building on solid rock. The wall is completely backfilled on the sides and back and the front has 5layers of bricks covered. I used the stones that came out of the hole to do this. and then covered it with the sand that come out and topped it with garden soil for the plants.

The ground here is impossible to dig deep in, the areas name is Klipkop and was farming land that was too rocky to be farmed so it was cut up in plots and sold off. Our neighbours had to drill and blast with explosives to make their pool.

I got an the local engineering shop to make me a heavy "wakker" and compressed the base really well before laying the concrete. I also did use the mesh and 10mm rebar on the base but not on the walls.

I agree that the joint between the base and the wall is a weak spot, i had the plasterer make the bottom curve up where it joins the walls to try and add some protection. And when I did the touch up plastering I paid special attention to that area.

They made the concrete on to 40mPa with 9mm stone and I used PPC made to the strongest suggested mixture on the bag. I wanted to not plaster the bottom and just smooth it out, thats why I went with 9mm. but changed my mind later.

Only afterwards I came across the gem of pushing the bottom layer of bricks into the concrete base while its wet so they half in the concrete which would have given a lot more strength.

The pond is damn solid otherwise and I don't see it cracking so I'm very happy, if it does one day, well I'd look into fiber-glassing it.

Would love to build another one and attempt a hand packing. What scared me was making the mesh and rebar go up the sides and packing above the level of the ground. Was just picturing the cement all level and hard in the bottom with no sides and having to jack hammer it out, lol.

 

Actually Dan... now that you mention it.. I forgot you mentioned you were on rock. That actually makes a HUGE difference to the scope.

The solid rock would prevent future movement. I did notive the heavy backfilling, so that didn't concern me at all.

All in all... I think you did a good job. Had I not forgotten about the rock.. I wouldn't have made my suggestions.

 

Nice ponds DanH,and thanks for the help on MyBB.

 

Cool Zoom, the base and wall joint bugged me too though.

But just over a year later and no problems at all.

I'm really keen to build another one. Anybody got a spare R50k in CT and a...lawn?

Cool man, taking your advice to post some of my systems :bigsmile:

 

well your pond is most impressive ,so where can i get some pics of your tanks?

 

Very cool indeed.. If you ever sell the house you will have two pools

 

In time, in time. lol

Yeah lol. I'm thinking why can't I stop using chlorine in the pool and add a bio filter?

 

Very nice Dan!

Let me know when those koi reached a decent size so I can rip out the old fishing rod

 

40 koi in a 20 000L pond is WAY over stocked. i have 14 fish in my 28 000L pond

Is the pond fiberglasses or painted with that super laykold roof sealer stuff?

 

Painted with 3 coats of Abe super laykold. The fish are still small. If stocking becomes a problem I will give some away. They seem to be very happy at the moment and the water quality is good. I'm sure your 14 are giants.

 

You are in for a very nasty suprise. Super Laykold is a roofsealer - i dont care that ABE says on their containers - it cant cope with the presures of a koipond. It starts to go 12 to 18 months after you filled it with water. The guys that i bought my place from also did a DIY job on the koi pond - the pond had an auto top up so no one noticed - leaked something like 16 000L a week!

wrt to the koi - i always only had 14 fish in the pond - from 20cm up to their current 80+cm size. If you keep that many fish in a pond you WILL have stunted growth

 

Will see how it goes man. On 14months now and its still perfect. If it needs to be done I will fiberglass the pond one day. What sealer should I have used?

There will always be more dominant fish that are more aggressive when it comes to eating and outgrow others and some that are shy and don't get much food and grow slowly. I don't mind this, I think the way nature works. Sure they are not so closely packed in nature, but then they also don't get a variety of pellets at least 3times a day in nature either,