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A series of educational articles and snippets of information about koi and their environment that you may find interesting and helpful

The case for algae in koi ponds
Koi keepers usually dislike algae and do their best to eliminate it but is algae the menace that it’s normally portrayed as or does it have any benefits for koi or for the koi keeper?

SchoolWinter Feeding
Have you ever seen notices alongside natural lakes warning the fish not to eat when the temperatures are low?  Me neither.

Yet still throughout koi keeping circles there are warnings that feeding your koi when water temperatures are lower than about 10°C will do them harm or possibly kill them.
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Aerating koi ponds
Why do we aerate a pond? The obvious answer would be to provide the fish with oxygen but, to understand what aeration really does, we need to think about what actually happens when we use an air pump to blow bubbles under water.

How does soft or hard water affect koi colours?
Water in Japanese breeders’ mud ponds doesn’t come from springs fed by water that has percolated through the ground, it comes mainly from snow melt or rain water that collects into rivers running off of the mountains and so it has very little contact with minerals in the soil and is, therefore, very soft.
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Three second memory 1 (376)Koi respiration
Water is caused to flow through the gills by the expansion and contraction of the buccal and the opercular cavities.  The mouth and opercula don’t have to entirely close for their valves to operate but, to ensure that the efficiency of the one way pumping action is maintained, they have to close sufficiently to allow their valves to be able to fully close and prevent the back flow of water during the respiration cycle.
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Aeromonas alley
A reason to have a heater on a pond is to prevent an effect, sometimes called aeromonas alley, which is due to the falling efficiency of the koi immune system when compared with the activity of pathogenic bacteria such as aeromonas at low temperatures. Opinions vary slightly as to the precise temperatures, but in general, aeromonas alley can be described as follows:
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Swan mussels
Swan mussels are sold as “an aid to filtration” because they filter feed on planktonic algae (green water) but they produce larvae that are parasitic on fish. Depending of the size and maturity of the adult, the larvae may be released in hundreds or hundreds of thousands at a time.

The larvae, called glochidia, are released into the water through the adult females’ exhalent siphon and sink to the bottom or are scattered by water currents. They can open or close their shells but cannot move independently so, once shed by the female, the glochidia must find a suitable host, usually within 24 hours, or they will die.
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Calculating pond volumes
We need to know the volume of a pond when it comes to adding a medication for the obvious reason that it is essential that any medication is added at the recommended dose rate.  Too little may not be effective and too much may be harmful or possibly even fatal.

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pH stability
pH and KH levels are probably best considered as two parts of the same parameter.  Koi can adapt to any pH between 7.0 and 8.5, but if the pH changes too quickly, they will become stressed.  The pH should be kept within this range and also not be allowed to vary by more than 0.2 per day.  If greater variations than this continue over an extended period, the fish’s health and development will suffer.
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Copper in algaecides
Copper isn't only poisonous to algae at low levels but it's also poisonous to freshwater fish, such as koi, at slightly higher levels. The manufacturers of copper based algae treatments rely on the user dosing the pond to a level that is poisonous to algae but not immediately poisonous to koi.
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Plumbing bypass circuits around equipment explained
Sometimes the manufacturer’s maximum recommended flow rate through a piece of equipment such as a heat exchanger, heat pump or UV clarifier is lower than the desired flow rate for the system as a whole and a bypass has to be fitted to divert some of the flow around it. With very little effort, friction loss can be used to make the bypass more controllable and therefore more effective.  These diagrams show how this may be achieved.
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