Q. I am digging a 20 x15 x4' deep Koi pond in clay soil. I plan to pour a concrete bottom and have footings around the perimeter to support the walls. I want to use a liner to help prevent leakage. When should the liner be installed, before or after the concrete is poured?

A. This is a very large pond and I am concerned that it is only 4ft deep. Ideally it should be at least five feet deep and preferably six feet deep. This is particularly important if you do not live in the South of the UK.
If you deepen the pond then with the fifteen foot wide pond it is very difficult to catch the fish even with a long purpose built koi net. I would suggest not wider that 12ft or a maximum of 13 ft.
If you put in a six inch thick base then the concrete walls can be built directly on the base without extra footings. After the base and walls are completed then the liner is laid inside and then passed over the top of the walls just above the water level. Coping stones or rocks can then be cemented on top. This type of construction can be seen here or here.
You can use a flat sheet of liner, but it is better if you get what is known as a boxed liner. This is shaped to the size of the pond and vulcanised so that there are the minimum of creases.

Q. I intend to put a pond in my back garden next year and am at the planning stage at the moment, and I hope to keep goldfish and 6-8 koi in the pond. My initial thoughts are as follows:
1. Size: 10ft long x 8ft wide x 4ft 6in deep.
2. Position: Full sun from 09:00 to 17:00.
3. Construction: Liner I'm afraid, just cannot afford to make it out of concrete blocks and fiberglass.
4. Filter: Cloverleaf Genesis 4500, sited out of pond and pump fed by Cyprio 1000 gph filter pump, TMC Pondclear Pro Clear 30 UVC sterilizer, Hiblo 20 air pump. Winter feed to filter will be by mid water position Cyprio 350gph pump. Seperate drain for vortex unit and common drain for remaining 3 chambers, note all chambers will have isolating slide valves. Return to pond will be gravity feed either through an ornamental pot, or is this possible, through a venturi.
Please feel free to make any criticism that you think would help me out. I would like to gravity feed the filter system, but the only place I can site it is next to a 6ft high brick wall and I am worried that I may disturb the foundations when I excavate the area to house it. 

A. General comments to his question are as follows:-
1.The size seems OK. I would make sure that it is at least 4ft 6ins deep, and preferably 5ft especially as you live in the Birmingham area.
2. With full sun all day you may need to consider some type of shading during the summer months.
3.This is not a problem. Make sure that you get a good quality rubber liner. These should last for about 20 years if treated properly. You should include a large concrete collar around the pond (before digging) to prevent the walls collapsing when people are standing near to the edge. The sides of the pond should also be sloped slightly.
4. This seems OK. I have no experience of the Cloverleaf filters. Your pond will be 2,250 gallons without filter quantity if the pond is 4ft 6ins deep, and 2,500 gallons if it is 5ft deep. For this reason and allowing for a turnover every two hours I would recommend a pump of at least 1,200 gals/hr, and preferably 1,500 gals/hr. Pipework will reduce the pumping capacity especially if the filter is above ground.
A Hiblow 40 is only slightly more expensive than a 20 and you can always use the extra capacity.
You do not mention a bottom drain for the pond. I consider this to be essential and the drain can go to waste.
Another item well worth considering is a power skimmer. The small ones for a liner are only about £35 and you can always connect a pump to it later. It certainly clears the pond surface and gives a much clearer view of the fish.
The height of the outlet of the filter will be high enough to run a venturi under gravity. It is possibly better to construct one yourself so that you can adjust it to give the best performance. A waterfall or ornamental pot can also be used. You could install both and by fitting a change-over valve can then use the one you want. It is much better to have the filter gravity fed as the pump liquidisers the solids and makes it almost impossible to filer them out. It may be worthwhile getting as compenent builder to examine the wall aand give you an opinion.

Q. I'd love to block and fibreglass my new pond however as it will be fairly big 22ft x 12ft x 6ft deep (4 under and 2 up) my finances won't stretch to that as I want to spend more money on the 'water quality' side of things this time (i.e heating / filtration etc).

A. Do you need to have a pond as large as this? This will work out at approx 9,900 gallons plus the water in the filters which will be approx another 1,500 gallons. If you look through the list of ponds in the pond description of KOI CYMRU you will see that very few are as large as that.
With the size of pond you suggest it is quite difficult to catch the fish, and almost impossible on your own.
Then you have to think about the cost of adding chemicals and/or salt for treatment as this becomes much more expensive for a large volume.

Q. If I had my way, money permitting I'd turn the back garden into a giant pond but the wife would only complain she'd no washing line anymore.I reached the conclusion that where I'd love is a 22 x 20ft pond where the lawn is, but it wouldn't leave my daughter anywhere to play.

A. Anything bigger than 20ft x 12ft is in my opinion too big to manage, and difficult to net fish etc. Also with a large pond the cost of chemicals, salt etc gets prohibitive.

Q. I am about to construct a koi pond and I am seeking information as to the best method. The pond I envisage will be approximately 16' long, 6' wide and 5' deep.

A. The pond size seem OK, but if your garden permits I would suggest that it would be better to have a wider pond of say 8' rather than 6'. I feel that 14' x 8' looks better than a narrow pond of 16' x 6'. However it may be that 6' fits in better with the room available in you garden.

Q. At present my pond is in three depths of 18ins, 24ins, and 36ins. My plan for the new pond is to dig down another foot at the deep end and build up the walls around another 2ft. So 3 (deepest part) + 1 + 2 (walls) = 6ft, which is what I've had in mind since contracting the "koi bug".

A. This seems fine. By building the pond a few feet above ground has the advantage that you do not have to dig down so deep. A seven foot deep hole close to the house or a boundary wall is not recommended. Professionals would not do it without extensive shuttering to prevent subsidence. You also have the advantage of being able to sit on the wall, and you are also closer to see the fish. The fish also seem happier as you are not standing right over them as they only see your top half.

Q. I have 3 large koi and 11 spawned last year. What pond dimensions do I need to maintain them outside over the winter? Should I run my filter all year?

A. At the moment you have 14 koi, but like all of us you will probably aquire more.
I would say the pond should be as large as possible, but at least 10 ft x 8ft. Most koi-keepers in the US do not seem to have deep ponds, but I would recommend your pond is at least 4ft 6ins deep.
Yes the filter system should be run all the year round. You can use a smaller pump in the winter so as not to disturb the water too much, but it is important to keep the flow through the filter so as not to kill off the bacteria.

Q. I intend to build a pond 15 x 10 x 6ft deep. Fibreglassed. This would be the outer edge size realistically to enable me to build filters along the long edge and still have access to them without having to climb over the top. Filters 3 x 3 x (5 x 3ft) length. Does this seem OK?

A. The size seems ideal. Make sure that the surface area of the filters are about 30% of the surface area of pond. You must design the package to suit the pond plus the filters. Too many people design the pond and then ask about filters.

Q. My interest in a new pond was sparked by wanting to build something for the millennium.My existing space in the garden is the big circular lawn and a circle would probably look best,is a round shape more difficult to build? Or what about a giant 2 shape?

A. You can have a circular pond, but I personally think a better idea is an oblong pond, possibly almost square with big radiused corners. A round pond can be built using 18 x 10 x 4 ins blocks cut in half and laid so they are 4ins high and 9ins wide. This can also be used for large radius, but if you need a sharp radius then you should use standard size concrete bricks as shown on my pages. You should keep away from sharp bends and difficult shapes as then you cannot get a good flow of water and some areas may had dead spots.

Q. Does a six foot deep pond take longer to warm up in the summer?

A. It probably does take longer in summer to warm up, but would also take longer to cool down in the winter. The most important thing about temperatures is to keep it as constant as possible without big fluctuations. With a shallow pond there can be big variations especially when we have a hot sunny day and cold nights. The larger the quantity of water then the temperatures do not vary so much over a short period. Koi cannot tolerate big fluctuations of temperatures.

Q. What is the price of building a concrete pond approx 14ft x 11ft x 6ft deep with the filter systems featured? I know the filters vary in materials-I'm looking for a figure so I know what to aim for in the future.

Q. I have calculated the capacity of my proposed pond to be about 2000 gallons which seems wrong when compared to some of your example ponds?

A. If the final size of the pond is 10 x 6 x 5ft deep then this is 300 cu.ft., and at 6.26 gallons to a cubic foot then this is 1,875 gallons. This is assuming that the pond is a cube shape, but in fact the base needs to be heavily benched towards the bottom drains, and the corners are rounded off. These corners are usually a triangle with the sides 12ins long. In this case the gallonage will be considerably less than 1,875 gallons. Some of our members ponds are suspect when it comes to gallonage, but their total figures include the vortex chambers, and the filters which can hold well over a 1,000 gallons in some of these systems. We always recommend that when filling the pond then the water is passed through a water meter so that the exact gallonage is known. It is a good idea to check the figures for the pond and filters separately so that you can alter the figures if you change the filter material. Even then some members seem to get confused when converting from litres to gallons. It is very important to know the correct gallonage when using chemicals in the pond.

Q. I can't seem to find an advert/supply for a flowmeter. I want the exact volume of my pond when I fill it. Would you know where I can get one?

A. Most clubs have at least one that they loan out to members when they are first filling their pond. There are a couple of advertisments for them in the Koi Carp magazine, and you can also get them from builders merchants.

Q. I've also realised that my idea of using the soil removed from my new pond to fill in the old is ludicrous as I reckon I've now got around 4 "ponds worth" of soil. Fortunately my 'helper' has offered to spend tomorrow filling a skip or two with the stuff!

A. It is amazing the amount of soil you do end up with. Full size skips are expensive, about £100 each in Cardiff (2000) so you need to budget for this before you start.