You would think your fish would be safe and cool in your pond during the summer months, but if your pond is too shallow this is far from the truth.
We as humans can suffer when the weather gets hot, but there are many things we can do to cool down, pond fish have one option, to retreat to deeper water where the water is cooler and has more oxygen, hot water holds less oxygen than cooler water.
A garden pond that is shallow will heat up a lot faster than a deep pond and if there is no rainfall evaporation will remove pond water making it even shallower.
With less water in your pond you will also have a problem with concentrated nutrients, this is great for plant growth but bad for fish, the plants and algae in your pond use up more oxygen during the night than they produce during the day leaving a fluctuation of oxygen levels.
You would think that clouds or shade would give your fish a rest bite from the searing heat, but it also has an opposite effect, less sunlight prevents plants from producing oxygen, less oxygen will affect your fish and the oxygen could dip down to levels where your fish could die.
If you have a shallow pond it’s going to be difficult to prevent your fish from dying, but there are things you could do.
Control the amount of aquatic plants, maintain the depth of the pond water by adding in more water, daily if needed, add more aeration.
You will know when there is a lack of oxygen in your pond, your fish will at the surface of your pond gulping in air, especially early in the morning when the plants have exhausted all the oxygen overnight.
The largest fish will suffer first as they need more oxygen, but this doesn’t mean all your fish will be effected, as fish die there will be more oxygen for the fish that are left.
The only thing that will stop fish dying in summer months is to have a deep area in your pond where they can go to cool down and get some much-needed oxygen from the oxygen rich water at the bottom of your pond.
If you have a shallow pond it might be time to redesign it with a deep area, if you are building a new pond you know what to do.