Q. The house we recently moved into has an old concrete pond that seems to be about 300 gallons (1135 liters) in capacity, if my math is anywhere close to being accurate. It has several cracks in it that are long but not open. Should we seal the cracks before filling the pond or use a liner? Any suggestions for making this pond into the centerpiece of the garden? It doesn’t seem big enough to hold koi, which I understand can reach more than 2 feet (60 centimeters) in length. Can you suggest some books about ponds? With spring right around the corner we would really appreciate your advice.
A. If the concrete is generally in good shape, then I would opt to fill the cracks. Many water-garden dealers sell special fillers for patching concrete ponds. You can also visit your local swimming pool supply store and see what they have in the way of crack filler. Most come with good instructions. Be sure to take the time to prepare the repair site properly — a little extra effort will spare you a lot of trouble later on.
After the crack is filled, let it cure. Then I would coat the entire pond with a good fish-safe waterproof sealer. This is where I get a bit nervous going to commercial pool outlets. Do yourself and your fish a favor and buy the sealer from a water-garden supplier. Many of the catalogue dealers carry high-quality fillers and sealers.
If the concrete is in poor shape, then I would opt to install a liner. This can be done quite easily and attractively. There are PVC-to-concrete adhesives available that allow you to bond a liner right to the concrete pond wall. Thus, you can avoid having an unsightly liner edge along the top of the pond.
To make this pond a garden centerpiece, think “lots of plants…very few fish.” If the pond is in a sunny location with five or six hours of direct sunlight, waterlilies will flourish. Choose one of the compact varieties and within two months you will have a marvelous display of flowers. The pond margins and outside edges can be planted with any number of bog plants. I really find iris to be exceptionally nice when it is planted around one-quarter to one-third of the back edge of the pond.
Alternatively, you can follow my mother-in-law’s approach and surround most of the pond with a perennial garden. I cannot describe how beautiful the flowers are, especially contrasted against the pond with its floating lilies. With good planning, this type of garden can be in bloom during spring, summer and fall. It is quite a sight.
In either case I would definitely include many pots of submerged plants to keep the water clear of algae. With the water clear, these plants will become a fascinating attraction themselves as they grow toward the surface.
The combination of abundant water and a variety of flowering plants guarantees that the site will become a magnet for all kinds of wildlife. This will greatly enhance the attractiveness of the pond because it will add sound, motion and surprise to the landscape.
In my opinion, 300 gallons is far too small for koi. Some good-quality fancy goldfish would be marvelous. If you limit yourself to two or three fish, you will find that they develop into beautiful, full-bodied, specimens — and you will not have to worry about pond filters. You will be surprised how a minimal number of fish in lots of water can be far more attractive than a pond teeming with indistinguishable fish.
Each year the number of good books about ponds increases. My favorites remain: Bill Heritage’s Ponds and Water Gardens and Peter McHoy’s Water Gardening.