Folks who live in areas of temperate weather all year long may find the following information difficult to fathom, but in areas where the temperatures go below freezing, consideration must be given to the "winterizing" of water-effects' basins and equipment.
A properly designed and built water feature will suffer no ill effects if maintained properly before, during and after freezing weather. This Section attempts to detail what can be done to resist the influences of winter on aquatic gardens.
Design & Construction:
The pond, fountain, stream, water fall and related equipment should be planned and built with the seasons in mind.
Water -Holding Basins: themselves should be as deep as possible with nearly vertical sides to resist cracking and even the possibility of being "popped-out" of the freezing ground.
The basin/s should not be drained and left empty, as this will present more risk of damage from crushing or being forced out of the ground then leaving the water in.
An old trick to prevent breakage from expanding water is to place a bucket or barrel or two into the basin(s) with a few rocks to keep them weighted down. Freezing, expanding water/ice will crush these containers first; before splitting your pond.
Equipment: Pumps, filters and plumbing must be protected from freezing, expanding water that will damage them. If steps are not taken to preclude the water becoming ice, the water must be drained from the plumbing and pump(s) and electrics secured until the season changes.
Equipment and plumbing should be situated near a warmer area, perhaps a structure, away from wind-chill, possibly within a housing, below ground level to conserve and concentrate heat.
If there are ways to keep some or all of the equipment running without the fear of bursting from freezing water, it should be left on during the cold season. A small auxiliary, submersible pump may be useful; as well as a vibrator-type air pump with a mechanical diffuser if run continuously.
Adequate maintenance through the summer and fall, removing muck and organic matter goes a long way in preventing low/no oxygen problems from oxidation of organics.
Livestock: If your pond is small and with few fish(es) and/or plants, the most appropriate technique may be removing the livestock and relocating it to a filtered aquarium, trough or kiddie pool in the garage or greenhouse for the winter. If not....
Fishes: Koi, goldfish, natives and other cold-water fishes may over-winter in your system; providing that some of the surface
area does not freeze over completely. If your fishes are fat and healthy in the fall, their metabolisms will be depressed enough accordingly to prevent mortality. The rule with dealing with livestock especially during the winter is the less disturbed the better. Instances of high mortalities are almost always attributable to poor design, overcrowding or inadequate cleaning before the cold season; or handling them after.
Livestock should not be fed below a temperature of 50 degrees F.; The fish may seem interested and eat, but be unable
to use the food and consequently the water will be fouled. Partial water changes should be of small volume, if any, infrequent and literally dripped refilled. Prior to cold water hibernation your fish(es) should have been well fed, checked for disease and disinfected if necessary.
Should be trimmed and kept to a minimum during the winter season. This is especially so with fish present as rotting vegetation will quickly deplete oxygen levels.
Hardy Lilies: can be left in the pond as long as their roots and tubers are not allowed to freeze. Don't know if they will? Remove them and store per Section D) i) a).
Tropical Lilies: are uprooted and stored damp and cool in plastic bags & replanted in Spring.
Others: If freezing goes down to their roots; remove bog plants and flowering aquatics and store them in your basement, garage or protected patio. Aquatic plants must be kept moist. Use wet towels and trash can bags and check and re-water them periodically.
What To Do With The Water:
Absolutely nothing if possible. If you've arranged your system such that some of the surface stays liquid and your equipment can run regularly/daily without the risk of freezing, don't worry. Biological systems can tolerate a wide range of conditions, even down to almost freezing, just not too-sudden changes.
To Keep the Water From Freezing:
1) Covering most of the surface. Plastic (polyethylene or PVC) is the most cost-effective in mild winter conditions. Some writers suggest clear film, but I prefer black. Some folks use boards and place straw, hay or other material on top of the liner or boards as well. Remove the ice and snow that accumulates on top of the plastic cover.
2) Electrical heaters, with or without thermostats can be purchased through feed stores (they're used to keep watering troughs fluid) or via aquatic garden outlets.
It may be economical to use a small spa or pool heater. An electric or gas unit may be plumbed in-line with the rest of your mechanical system.
Note: Any 110 volt electrical device used in or around the +water must be fitted with a Ground Fault Interrupter to prevent electrocution. Do not trust a circuit breaker with your life around water!
3) Heat exchange: Sometimes enough heat can be absorbed through the plumbing from the ground or another source to warrant using a "winter-bypass" line that will allow you to "pump" heat into your aquatic system by way of looping your circulating lines through a warm area.
4) A trickling garden hose can be utilized in some situations where the influent water is considerably warmer, overflow is accounted for and the tap water is not too noxious.
Some people allow the surface of their system to freeze over and try to prevent fish loss by periodically breaking the surface ice, releasing carbon dioxide, hydrogen sulfide, et al.. Don't do it. This is a very dangerous proposition for you and your livestock. Prevent complete freeze-over rather than risk injuring yourself or your fishes. The concussion from tapping of walking on the ice alone can kill fishes.
Water-freezing weather can present problems for aquatic gardens. These problems should be anticipated and the system's design, construction and on-going maintenance applied to eliminate damage or disaster. With a little planning and action, freezing weather will not cause you difficulty.
Harants, Ann. 1994. Looking ahead; cold front on the horizon. Koi USA 11-12/94.
Matsui, Yoshiichi, 1981. Goldfish Guide, 2nd Ed., T.F.H. Publ., Inc., N.J.
Meyer, Stephen. Frozen waters; there are a number of factors to consider when dealing with winter ice on ponds. AFM 1/91.
Ostrow, Marshall E. 1978. Winterizing goldfish. TFH 11/78.
Takeo, Kuroki, 1985. Manual to Nishikigoi, Shin Nippon Kyoiku Tosho Co., Japan.
Thomas, Virginia J. 1988. Winterizing koi ponds; help customers avoid cold-weather catastrophe. Pet Age 10/88.
Uber, William, 1988. Water Gardening Basics, Dragonflyer Press, CA.