Building
There are lots of materials for building a pond that you can choose from. These include; concrete block, preformed fibreglass, wood and flexible liners. All have advantages and disadvantages depending upon location and style of pond desired.
Concrete offers a long life span but requires lots of planning and measuring. Preformed you know exactly how it will look, but make sure you measure it out before you buy - they often look much larger in the shop than at home! All ponds that go below ground level will need lots of digging and remember that the excavated soil needs to go somewhere!
Waterproofing your pond is usually done with one of three methods; fibreglass, liner or render/pond paint.
Fibreglass is most popular because of its clean lines and flat finish. This allows easy cleaning of the pond via filters, bottom drains or vacuum.
Liners can be difficult to fit to unusual shaped ponds or those with protruding angles. Debris can accumulate in the folds of the liner and if not removed this can affect the water quality as it decomposes.
Whilst thinking of your design it would now be a good time to plan your window or windows. The method of waterproofing can affect the choice; four sided frames can be fitted to all types, but you can only fit a three sided frame to fibreglass or render. Windows can be made to measure from a minimum of 1ftx1ft to 8ftx8ft! The glass thickness is calculated based on the dimensions of the frame and the volume and pressure of the water it is holding back. MR Koi recommends using a laminated heat treated glass.
Something else to think about is how do you want your water to return to your pond from your filtration system? In a koi pond your returns are normally through mid-water (pipes) or top-water level pipe returns (a 'bakki shower' or an ornate cascade waterfall). In a wildlife or goldfish pond the return would probably be a fibreglass stone waterfall or fountain.
Remember that whilst waterfalls add oxygen content to your water they can also be noisy and create water movement which may drive your koi to deeper, quieter water.
Once you have designed the look and style of your pond you will now need to sort out some kind of filtration for it. This can be done in a number of ways; block built gravity filters, 'black box' filters, vegetable filters or more expensive filter units such as Nexus, sieves with bead filters or fluid bed systems. Consider housing your filtration units as this will both hide them and protect them from the weather.
You would probably need to talk to an expert to get the correct calculations to enable you to work out the best type of filtration for your pond.
Once you have your design you need to know how to finish the look of your pond. What coping stones will you use? Are you facing your pond with brick, stone, wood or render? Do you want a roof over your pond or a pergola? All these questions depend very much upon the landscape in which you will be building and how you want the pond to sit within it.
Finally you will need to consider the rest of the garden. It will probably look like a building site for quite a while. You may need to get some landscaping done and blend your pond in to your new surroundings.