Splash out

My vision of a fabulous garden pond has always been a big, white marble basin filled with absolutely clear, blue-green water. Nothing else.
From time to time I've tried to create this look, but have been defeated by drowned flies, rotting leaves, algae and, once, part of a dead hedgehog dropped in there by a passing harrier hawk.
When vigilance and artificial food colouring failed to maintain my pristine pool, I decided plants and fish were the only answer.
It's interesting how fond you can become of goldfish. They're not exactly chatty and they don't cuddle, but they do have personalities and I found it distressing when the asperger's cat (pictured) adopted that strange position for hours at a time until she finally managed to hook one out for a closer look.
The fish had to be re-homed and the pond languished, fishless, plantless and waterless, until I decided it could become a water garden.
For gardeners, creating a water feature or pond is a great opportunity to discover a whole lot of new plants. But as with garden plants, you do need to do some homework to find out what's likely to work. Otherwise, you risk creating the equivalent of an open drain.
If you have an existing pool or pond that needs a makeover, start with the inevitable clean-up. Take everything out, drain it, remove all the sludge, put aside any plants you want to keep, then scrub it. Rinse thoroughly and refill.
You need a plan before you head out to buy plants. Decide whether you want a lush, natural look or simple, classic style and buy accordingly.
Plants for ponds can be loosely divided into three main categories. There are deep-water oxygenators that can tolerate conditions from boggy grounds to depths of up to 60cm above their crowns.
Waterlilies are considered deep water plants, with tropical hardy and miniatures varieties available. The ideal planting depths can vary, so check the label.
Marginal plants are those that like to keep their roots in the water so they'll do well around the edge of a pond.
Bog plants like the damp and you should select these to position on the side of ponds for stabilising soil. Many bog plants will also grow in normal garden locations.
To maintain a healthy environment, you need to cover about 70 per cent of the surface of the pond with foliage. Otherwise, there'll be problems harder to fix than a few dead flies in the water. Algae, for example, will thrive if the surface of the water is constantly exposed to sun, so discourage it by shading the surface with floating plants and water lilies. Deep-water oxygenators will help too.
Failing that there are algaecides on the market that will clear the water. Organic versions are also available but need to be used regularly and take a few weeks to get on top of the problem.
A somewhat more technical solution is a UV clarifier, where the water is passed through a sleeve which contains a UV bulb to kill the algae. Blanketweed is harder to kill. It likes a high pH so if you have a concrete water feature or your pond is lined with river stones you're a target. You'll need to manage the pH and there are products available to balance it.
You can use an algaecide to kill it but it will come back unless you get the pH right.
If your cat has made keeping fish impossible you could be pestered by mosquitos.
The larvae like shallow, stagnant water, so a simple pump to keep it moving will work.
The best tip for minimising pond problems is to refresh the water as often as you think of it. Every weekend, scoop out a few watering cans full of water and use it on the garden, and top up the pond with fresh. It's a benefit for both pond and garden.

Top tip
Contact your local council or DoC office before you start your pond and find out what not to plant. Many water plants become invasive in streams and lakes if they escape from your pond.

What to plant

Choosing plants for your pond area will open up a whole new range of species you may not have met before.
* Golden moneywort has lovely  coin-shaped foliage that trails away from the centre. Can be submerged 30cm in ponds or planted in moist gardens.
* Pond pickerel is a lily-like plant that prefers water 5cm to 20cm deep. It has has lush green foliage and striking blue flowers on 80cm stems all summer.
* Native water ranunculus is small and lace-like, with green scalloped leaves and tiny yellow flowers. Also also grows on muddy margins.
* Vietnamese mint is a fragrant mint used in Thai food. It spreads 90cm across the top of the water.
* Tall Egyptian papyrus  is a popular pond plant with long, slender stems and exotic green plumes.
* Umbrella grass - hardy plants for cooler climates that will happily live submerged 5cm-20cm in a pond.