Planning Your Pond
Before you start to dig, there are some important things to consider about where you are going to put your pond, what shape and size to make it and the liner you should use.
Choosing a site
First, make sure you don’t have your pond in the lowest area of the garden; runoff from lawn pesticides, driveway salt and garden fertilizers can pollute your pond. Try to put your pond where it will get as much sunlight as possible, less than 6 hours of full sun severely limits bloom production on most aquatic plants. An area that is already marshy (from a high water table) is not usually the best place to put a liner pond. The water tends to come up under the liner, creating a bulge in the middle of the liner.
Try to avoid areas with lots of trees. Trees are a problem for three reasons. First, because they shade the pond, remember most aquatic plants need AT LEAST 6 hours of full sunlight to bloom. Secondly, trees mean that there will be a lot of roots to dig through and, depending on the quality of the liner you choose, they can also damage your liner in the future. The last (and most important) reason to avoid trees is autumn, or more appropriately FALL… the leaves will mean endless cleanup as they fall from the trees, try to get as far away from them as possible. If the leaves are left in the pond all winter, your water in spring will look brown, and the rotting leaves can cause major algae problems. They also may cause fish kill over the winter.
Shape and Size
In choosing pond size, remember that smaller does NOT equal easier, in fact, the larger the pond, the easier it is to achieve a natural balance and the less algae problems usually occur. Try to plan a simple shape, a kidney shape is popular, and gives a natural look. Avoid narrow sections and bays, the water will not cirulate well and may cause problems.
Examining the site
Lay out the shape you have chosen with a garden hose, then look at it from different angles. Don’t forget to check the kitchen/livingroom window. Sometimes moving the pond over by two feet can make the difference to the view from inside the house and it is a lot easier to move the pond BEFORE you dig it! This is a good time to watch and see if you will get enough sunlight. Try to think about what might reflect in the pond… if you have a large mirror, lie it in the hose outline and have a look.
Two feet deep is the MINIMUM recommended depth, ponds less than 18″ deep= algae problems. For our climate (Canadian zone 5, USDA zone 4) 2 1/2 to 3 feet is needed if you plan to overwinter fish and waterlilies in the pond. Check with your municipality and insurance company to see if there is a depth over which you need a fence. The depth of the marginal shelf should be nine inches.
Type of Pond
The advice we have given here is aimed at installing a liner pond but most is also applicable to a concrete or rigid preformed pond. If you install a concrete pond, make sure you seal it and then treat it to neutralize the alkalinity from the concrete. Preformed ponds (sometimes called molded ponds) tend to be more expensive than putting in a liner pond, and are seldom deep enough. Preformed ponds are also difficult to install, you must make sure that the shape of the hole you dig EXACTLY matches the shape of the pond or it will shift and you will have to reinstall it.
When choosing a liner, take a close look at the warranty period, it gives you a good idea of how long the liner will last. The two most popular liners are PVC (vinyl) and EPDM (synthetic rubber). There are major environmental concerns in Europe about PVC as it is the only type of plastic that can not be recycled and causes problems in landfills. PVC has a 5 to 10 year life span and tends to be more expensive than the same thickness of EPDM rubber liner that comes with a 10 to 20 year warranty. We recommend EPDM fish-safe rubber liner… don’t confuse this with roofing EPDM, fish-safe liner is made with virgin material, roofing rubber contains heavy metals and will kill your fish and stunt your plants. EPDM rubber is always flexible, even in cold weather, is easily patched but is very hard to puncture since it very strong.
Choosing the correct material for building your pond is probably the most important decision you will make for your pond. Just imagine having to take out an old liner to replace it when the pond is mature with blooming plants and pet fish which have to be safeguarded while you repeat the whole original installation process!