Cold Weather Problems

Had the immortal bard William Shakespeare been a dedicated KoiKeeper, he would be writing to us today with the warning “Beware the Ides of January”.

Over the past few days, the weather has got very cold. Conditions have again been below those usually expected. On Friday, I raised a couple of our own Koi to check and after about 10 minutes, I was surprised to find that both the net and Koi sock had frozen to the ground. I had to use a hose to un-freeze them.

We are receiving several calls/ emails a day with regards to Koi laying on their sides. Most cases appear to be temperature related but some are due to other causes which we will discuss later. Let’s look first at the cold weather problem:

When your pond water cools down, the metabolic rate of your Koi reduces rapidly and as the oxygen demand is far less, the respiration slows. The beat rate decreases from about 120 beats per minute in warm weather to 40-50 b.p.m. and .the swept volume of the gill movement (the amount it opens) also reduces. Once the water temperature gets below 2- 3 deg.C., your Koi are at risk. At this temperature, all the life giving functions have slowed right down and survival is a challenge to any Koi who is not in a good healthy condition. One major problem which often occurs is chilling of the swim bladder which impairs the buoyancy of the Koi, and their balance is affected. The only way to correct this is to warm up the pond water slowly, if possible or alternatively, transfer the affected fish to a warmer environment (i.e. quarantine tank). If the Koi is left on its side, the fish will deteriorate and often, fungus takes hold. By warming the water up to 5 deg.C, in a large number of cases, the Koi will regain equilibrium. Should Cold Weather problems occur, you can take immediate action by:

1 In an emergency, if the pond water is below 4-5 deg.C. and the fish are on their side, undertake a 25% water change. Your tap water will be in the region of 8- 9 deg.C. at the present time. Remember to run the hose for a few minutes first to allow it to warm and to use a purifier or de-chlorinator. It is a good idea to drain the hose and store it in the garage or shed otherwise it may be frozen the next time you try to used it.

2 Put in a small heater (if the budget allows!).

3 Bypass any waterfall to avoid further cooling.

4 Turn off any fountain (provided it is not the only source of air)

5 Turn down the air but make sure you leave a reasonable amount in your pond as there is still an oxygen demand in the winter by your Koi, filters and system.

6 Cover the pond to reduce heat losses but make sure that you leave an air gap of at least 4” and ventilate under the cover.

7 Should the surface freeze, melt a hole in the ice. Do not smash a hole through the surface.