Three Common Materials for a Garden Pond

Ponds need to be watertight and, within reason, it doesn’t matter how you achieve this. Today there are three main options:

Prefabricated ponds Rigid moulded liners made from vacuum-formed plastic are the cheapest and they usually come with built-in shelves. They are relatively easy to install, and many people like them because the shape is predetermined, but they are fairly shortlived. PVC-based and rubberized compounds are available; these are slightly more expensive, but are longer lasting. Moulded fibreglass pre-formed liners are the longest lasting of all, but are not so easy to find, and are more expensive when you do.

Flexible liners These are basically lengths of waterproof sheeting, enabling you to build a pond of any shape or size. More planning is required, and calculating the amount of liner you need is not always easy. Lined ponds are ideal for informal schemes, since the sheeting will fit most shapes and contours, albeit with varying amounts of creasing. Many raised ponds, which at first appear to be constructed entirely of bricks and cement, are actually lined inside. The best reliability comes with rubber sheeting known as butyl, but PVC and LDPE (low-density polyethylene) sheets are also to be recommended. Buy lengths with a guarantee of 20 years or more. Polythene is common at the cheaper end of the scale, but it lacks pliability and becomes brittle after prolonged exposure to sunlight, so is best avoided. Finally there are ‘geotextile’ liners, which are rubber-based liners impregnated with sodium bentonite. These are self-healing liners -if they sustain a minor puncture, the bentonite will plug the hole.

Concrete ponds Concrete was the main choice years ago, but is no longer favoured because making a satisfactory concrete pond takes a great deal of skill, time and hard labour. Achieving the right mix, applying it correctly and keeping it workable, are tasks that many beginners get badly wrong. Yet, properly designed and constructed, a concrete pond can be elegant and have an air of permanence unequalled by other materials.

Safety must be paramount at all times, as any water feature is a potential hazard. If a pond is big enough for plants and fish, chances are it is also big enough for a child to fall in. So safety must be a major consideration if children are likely to be present. Choose a site with all-round visibility, so that you can keep an eye on children while they are playing in the vicinity.

Barrier fencing is an obvious safety measure, and it need not be unsightly. Picket fencing is certainly an effective barrier (and can look quite attractive, too) but it must be at least 75cm (30in) high. If end posts are slotted into sockets at ground level it need not be a permanent fixture. Both metal hoop fencing as used in parks, and chain link fencing as used around school playgrounds, will merge into the background greenery and be less obtrusive if painted dark green. Heavy grilles placed over the pond might save lighter children from taking a dip, but this is hardly an attractive element for a garden pool.

The barriers mentioned above will also protect your fish from cats and herons – the two main enemies of the outdoor fish keeper. But as far as children are concerned, to be honest, if your pond poses a permanent risk to them, it is better to be without it until they reach an age when you do not have to watch them constantly.

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