Hi Colyn,
One of the things that has been upper most in my thoughts in my 37 years of koi keeping is to help koi keepers be succesful.
I suggest you discuss your set up with a wider range of people before you start the filtration. It could save you a fortune and a lot of headaches in the long run.
I agree you do not need some of the fancy commercially available sysems on the market. Your system is too big for this.
On your size pond there is only one option – build the filter system yourself. Purchasing filter systems will cost you a fortune and will in all probability be inadequate for the capacity.
1) I do not see the necessity of two 1000 litre tanks. What size piping will connect hese tow tanks. Your whole system is a biological filter (convertor) This includes the walls, floors etc. These two tanks will restrict your flow rates. In your system you need to have the maximum flow rate you can have to get as much of your water through the filter system in the shortest time. So some alternative chamber designs will work better. Even stone filter (correctly designed) will be cheaper and work better.
2) Ignoring the fish you have built an enormous organic farm. The amount of algae the will be produced in the ponds will surprise you. Where will it go? How will you eliminate it from the system? Settlement in the shade cloth netting is fine but it wherever the algae is it dies and decomposes. So without the fish you have literally kilograms of algae sitting somewhere rotting. This extracts oxygen from the system and adds ammonia.
3) Shade cloth netting works fine for a season or two. Then it clogs.
4) The veggie pond will work but will need maintenance in a few years time. The roots of plants collect the solids in the water. Over time in inner most parts get cut off from the water and go anaerobic producing a foul smell. This is hydrogen sulphide and is very toxic to koi in very small amounts. You will hav eto keep an eye on this over the years.
5) The placement of the bottom drains? The slope of the floor will not help much to move the settled solids out of the system – the movement of the water as well as the koi feeding on the bottom will do this for you.
6) Every part of your system needs to be designed to be easy to clean for the above reasons. This includes parts such as settlement chambers, discharge boxes etc.
7) The only way to clean a filter properly is to totally drain it and flush it out – this includes the bioconverters. You must be able to shut off the water flow and drain the chambers.
8 ) These principals apply to any size filters, of any design.
9) What size pump/pumps are you thinking of using? What size piping to and from the pond?
10) I presume the lowest pond will be a large collection dam? Each pond will overflow to the next? Where will the solids that are surfaced skimmed from each pond be removed from the bottom pond? If the bottom pond is not skimmed as well you will end up with a lot of scum and dust on the surface of the lowest pond.
11) Will you have a stream or waterfall to introduce oxygen into the water?
12) Just a thought on the size of your biofiltration (bioconverter). You want as much as possible. That’s OK but you have a very large capacity and unless you want hundreds of large koi in your system I suggest you place more emphasis on the mechanical side of the system. The reasons are simple. You want clear water to see your koi (and so do the birds). The biological part of the koi pond takes places everywhere not only in the filter chambers. Once going the biological part of a koi pond works easily and is very efficient at converting the ammonia from the fish and dead algae. This is provided the chambers as correctly designed. If more emphasis is placed on the mechanical side things like flow rates, maintenance, internal design of filter chambers becomes more important.
13) You have a wonderful opportunity because you are not limited in the space available for your design.
14) Where will the water drain to in the event of the pump/pumps shutting off? Is each pond or chamber interconnected? You have a natural slope which is great as it can be used for waterfalls and streams. But consider where the water will end up when the power goes off.
So I suggest you discuss your ideas a little more. Its much cheaper to use a few pieces of paper for diagrams and discuss ideas than to build and be sorry.
There are many solutions to the basic problems of a koi pond but you need to follow some basic principals in each and every step of the way.
I hope this helps.
Regards,
Chris