What happens to Koi in Spring? As temperatures start to rise koi come out of “semi hibernation.” This occurs as Koi are “endothermic poikilotherms” which means their body temperature reflects the ambient temperature of their surroundings. At above 5 degrees centigrade, Koi should start to show an interest in food, they can be fed a low protein food i.e. wheat germ, give this sparingly – be aware of cold snaps at night, food will not be properly digested at low temperatures unusual weed pipes.
If the filtration system has been turned off for the winter, there will be no micro organisms living in the filter media, with the filter running throughout the winter time, the bacteria will have reduced because there is no ammonia (NH3) in the water because of zero feeding, the cold temperatures this will reduce the bacteria population, for these reasons feed with caution. Now that your Koi are becoming active, it’s time to check the overall cleanliness of the pond, is the bottom of the pond free from debris, silt etc. this can harbour harmful bacteria and parasites and in the summer, with the warmer temperature this will reduce oxygen levels.
Algae will also start to grow in the pond; there are two main types of algae, which pond keeper will have to deal with…
1. Single cell algae, this causes “Green Water”, this is caused by the combination of sunlight, phosphate and nitrate. The solution is a UV Filter. To determine the size of a UV Filter, the rule of thumbs 10 watts per 1000 gallons, this is for a semi shaded pond; ponds that have sunlight all day will need more watts per gallon. Now is the time to change your UV Bulb.
2. Blanket weed, this is the long stranded green “string like” algae which grows on the pond wall, floor etc. The solution is chemical/natural treatments, the two we recommend are ‘Cloverleaf Blanket weed Answer’ and ‘Evolution Aqua Stop Blanket weed’ these are both excellent products, but always remember every pond’s water chemistry is different. Algae in moderate levels won’t cause problems to Koi, but in large amounts can cause pH shifts, can reduce oxygen levels and block pumps, pipes and filters.
When the temperature increases, the first to become active are Pathogens, Parasites, Bacteria, Fungus etc. These react to warmer water quicker than your koi’s immune system, to slow down this activity, salt is used by some Koi keepers, and ½ oz per gallon is the recommended dose. The salt increases the mucus on the fish, which is the first line of defence for Koi, the downside of this is the bacteria in your filter will be ‘knocked back’. A Filter Start chemical could be the way forward. When feeding, fish waste is produced, ‘Nitrification Cycle’ bacteria needs boosting.
Water Changes, during the winter the only water changes which should have occurred are natural….. Rain Water, so for approximately 4 months your fish have been breathing in and out the same old water…Time for a change!! A 5% water change would remineralise the Koi environment. Don’t forget to test you water parameter NH3, NO2 and PH. You should be able to purchase a test kit from your local Koi dealer or from a good online supplier.