DIY Pond building

Any aquarist who is fortunate enough to be able to keep fish inside in an aquarium and outside in a pond soon starts to see the many parallels between keeping fish in both environments. The fish are fed an artificial diet, the water is circulated through a filter by a pump and the water quality parameters are measured routinely. But when it comes to their installation, an aquarium and pond are worlds apart.

Outside we can enjoy the freedom of pond design, designing and creating the shape, depth and overall volume of our pond whereas an indoor aquarist is virtually limited to aquaria off the shelf, where any shape is available, as long as it is made with straight sides! Wouldn’t it be great if we could build an aquarium like we can a pond – into any shape we wished.

With a pond, we have both options. We can go for the off-the-shelf instant pond approach, or the no-holds-barred method for the more creative. There is obviously a market for both approaches but which is going to be the better one for you?

Preformed pools.

There are two or three different types of preformed pool available, offering us differing degrees of rigidity, lifetime expectancy and size. The most basic of preformed pools are made from a very flexible thin plastic that is moulded into various shapes, usually holding up to 70 gallons. Tougher high-density polythene pools offer improved strength and puncture resistance and although they are semi-rigid they are capable of holding nearly 200 gallons comfortably when buried. The most durable of the preformed pools are the rigid glass-fibre pools which are also the most popular. Available in a range of volumes from a tiny 30 gallons to over 1000 gallons, these strong and durable ponds are built to last a lifetime.

Just as when we are choosing an aquarium, we are limited to the range of ponds that our retailer can supply. It is rare for an aquatic outlet to stock the full range and you might have to be prepared to wait a few days while your particular is ordered. Before looking at ponds, you will have a good idea of the area of the garden that you want to give over to water. This will immediately allow you to focus in on the preformed ponds that are the most appropriate for your plot. The models in your size range will offer different depths, and shelving arrangements for marginal plants, some of which may be more to your liking than others.

If you intend your pond to be a formal, regularly shaped pond then rigid fibreglass ponds offer you many benefits in that you do not have to dig a hole of the correct geometric shape or dimensions. Just make one large enough to take a pond, back-fill accordingly and hey-presto, you’ve created a perfect formal pond without using a set square or compass.. If you have chosen a pond over 300 gallons in volume you will not be able to get it home in the boot of your car so make sure your retailer can deliver it when you want it (and hopefully free of charge).

Installing a rigid pond could not be more straightforward.

1. Dig a hole a little bigger than the shape and depth of the pond.

2. Place a loose covering of moist sand in the hole.

3. Place the pond in the hole, ensuring it is level and begin filling with a hosepipe.

4. As it fills, start to backfill with loose soil or more sand, checking regularly that it is level.

5. Keep the remaining spoil to one side with a view to using it to make a raised rockery and waterfall.

Flexible pond liners.

Pond liners offer us flexibility in both the material we use and the extent to which we can design a pond. Long gone are the days when a heavy-duty polythene sheet was the method for lining a pond. Today’s pond liners have gone the way of pond pumps in that they have been re-engineered to meet (and indeed exceed) our expectations, with many pond liners now being sold with a lifetime guarantee.

In a similar fashion to rigid ponds, flexible pond liners are available in a range of qualities that reflect their durability. Made from materials such as PVC, rubber and butyl rubber and more recently hi-tech composite materials, which to be competitive, are guaranteed for life and as long as they’re installed correctly.

Liners are sold either pre-cut and packed or off-the-roll, depending on the size of the liner. Take your three-dimensional pond measurements to your retailer who will then work out the area of liner you require. This is also a good opportunity to plan out a waterfall. One particular advantage a liner has over a preformed pool is that you can lay the liner to incorporate a waterfall, making the cascade in effect an integrated extension to your pond. So even if your waterfall leaks (as is often the case) as if by magic, all of the leaking water still returns to the pond.

Once cut off the roll, your liner should easily fit into the boot if your car (but may be deceptively heavy). Because of a liner’s flexibility, more care must be taken when preparing your hole to protect against protruding stones or invasive roots. If the liner is going to last over 25 years, you cannot expect it to do so while pressing down hard against a sharp object.

Prepare the shape and depth of the hole as desired (this time you’re the boss) and then cover the surfaces with loose damp sand or even special pond underlay. I have even used old carpet very successfully (but remember to check for any old tacks!). The liner will become very supple in direct sunlight making laying it far easier. Once you have laid the liner and attempted to reduce the number of creases, start filling the pond up, pulling and stretching the liner as it fills to reduce the creases further. Only when the pond is completely full should you trim off the excess liner, leaving at least nine inches overlap. Remember to leave an extensive overlap intact to underlay your waterfall.

Price comparison.

How much would it cost?

1. 250 gallon pond

Rigid Fibreglass 0.5mm PVC Butyl Rubber

‘Lifetime Guarantee’ ‘Lifetime Guarantee’ ‘Lifetime Guarantee’

8’ x 6’ x 2’ shelved 13’ x 11’ equivalent 13’ x 11’ equivalent

+ irregularly shaped

£239.99 £43 £100

2. 1000 gallon pond

Rigid Fibreglass 0.5mm PVC Butyl Rubber

‘Lifetime Guarantee’ ‘Lifetime Guarantee’ ‘Lifetime Guarantee’

16’ x 8’ x 2.5’ shelved 22’ x 14’ equivalent 22’ x 14’ equivalent

+ irregularly shaped

£1000 £84 £224

In summary, each method of creating a pond provides us with different benefits depending on the nature of the pond. Both materials now offer a similar guarantee, with pond liners giving more flexibility with our pond design. We dig our hole first and then line it. With rigid ponds, we work the other way round, digging the hole to suit the size of the pond. Flexible liners can prove difficult to install in a formal shape (square or circular) whereas preformed ponds can create that effect perfectly and immediately. The choice is yours but with flexible liners you’re offered far more scope as pond designer and comparatively, they offer excellent value for money.

Kill blanketweed and string algae.