Ponds

A floating raft on top of a pond. No quite as exciting as my old quarry, but it looks good.

LURKING IN THE DEEP

When I was a youngster I was lucky enough to have a disused sand quarry at the bottom of my garden. Just a hop over the garden fence took me into a 50-acre wonderland of gold coloured sandstone cliffs left over from the glory days of the extraction. There were large dunes where we could hide and loads of really dangerous plant equipment had been left behind after the quarry closed, which gave us an enviable play park full of sharp rusty metal and old lorries to play on. We rolled down old conveyor belts, got trapped in large storage tanks and clambered up rickety 100-foot platforms that wobbled as we ascended the vertical steps to get a good vantage point to spot the rival gang members approaching. Oh, the days before health and safety. There were also six very large and very deep lakes with small islands in the middle of them that were made from where the sand had been removed. Home made rafts were scattered along their shores and with the aid of an old plank we would paddle out to our own sanctuary islands out of the way of the world.

The Big Freeze

In winter the quarry ponds took on a completely different use. I’m not sure if it’s the changing climate or the fact that these ponds were inland, but they seemed to freeze over for weeks at a time. Ice formed to the depth of about two feet in some places and the resulting platform was safe enough to drive a lorry over (not that we could ever get them going of course).

This year was about the first time in Inishowen I have experienced anything like those big freezes we used to get. My exploits sliding across the frozen water back then went unnoticed, unlike this year where the celebrities that went out on Inch Lake for a bit of fun ended up on the front pages of the local papers.

If these winters persist then we might have to rethink how we build small ponds in the garden, especially ones built from concrete or have fish in them.

Frozen ponds
Expanding water from freezing could damage the rigid structure of a small pond; especially concrete ones as this material is quite inflexible. Butyl rubber on the other hand can expand so this makes it more reliable and less susceptible to leaking. These are prone to leaking though through heron or stone damage or by any other sharp object poked into the side of the pond.

If you have sprung a leak in your butyl pond though I have a great tip for finding the hole.

Fixing a hole
Wait for a spell of dry weather or just allow the pond to keep losing water by protecting it from rain with a cover. At some point the water will stop disappearing, indicating the lowest point of the leak. Keep an eye on the water level if you have fish, the hole could be right at the bottom of the pond. The next step is to find the hole. Check around the perimeter of the pond at the level that the water has stopped dropping for any visible holes or tears. If none are visible, top up the pond with an inch or two of water and gently pour a cup of milk as close to the centre of your pond as you can get. It should be sucked toward the leak and you will be able to see the white milky trail. If you see no trail from the centre, wait for a calm day and add milk to areas around the perimeter. If and when you find the hole, you can patch it with a liner patch kit available at most garden centres or online. If the pond is concrete it will be a bit more difficult as cracks can be very persistent. Try making friends with a plasterer.

Fish
The quarry ponds were very deep and because of this all the giant fish and monsters that lived in the murky depths managed to survive the winter.

Fish swim deeper into ponds as the water freezes. If the pond is about four feet deep it will always have an area for them to swim about in and keep safe. After saying that, most fish can survive for short periods in shallower ponds as long as it isn’t totally frozen. Freezing isn’t always the full problem though. An ice-capped pond stops the normal gas exchanges between the water and atmosphere. Even when water temperatures are low, fish still continue to metabolise, requiring oxygen and releasing CO2. Other gasses accumulate under the surface and they can reach levels that can affect water quality, making it turn ‘sour’.

Releasing the gasses

To release the gasses thaw a small hole by pouring some boiling water on to the ice. Ice needs to be thawed quietly, without banging or breaking the ice with physical force as the pressure waves and noise can shock the fish. If the frost isn’t that severe but looks like it will last a long time, try putting a football on the water. When the ball is taken out of the water it will leave a small hole where the gasses can escape. If you have the resources there are heaters especially designed to rest on the water to stop it freezing. Sold with a float, the pond heater (usually 100W) gives off sufficient heat to provide a hole in the ice, with the same running cost of a standard light bulb.