Koi pond heater is an extra just like UV lights. UV lights make the water clearer but are not needed to keep your fish healthy.
Where a pond heater is an optional choice, I will let you decide if having one is really worth it, as it has good points and bad points.
But depending on where you live you may not need to even consider having a heater for your pond.
Good Points for having a Koi Pond Heater
If you live in England like me then you know as well as me it can get very cold for roughly 365 days of the year. OK OK OK!!!.... Maybe we do have a slight summer in the middle somewhere, but if you have a smaller pond and no moving water your koi could be under ice in freezing temperatures for long periods of time.
From winter to spring the water starts to warm up and this is where pathogens start to multiply just like any bacteria does. The Koi are not strong enough to fight them off causing disease. Also they could have sores from where they have sat still for so long under ice at the bottom of your pond which can easily get infected. So by having a heated pond you are removing this problem.
One huge reason why Koi keepers have pond but I feel is the least important is that if you have no ice through long winter months then your can view these beautiful fish any time and all year round.
Bad Points for having a Koi Pond Heater
Cold temperatures slow down all bacteria and parasites which we all know, that is why we have fridges and freezers to keep are food in. The food is kept cold and the bacteria stops growing or dramatically slows down decreasing the risk of food poisoning...
...Or we cook the food to kill the bacteria to make it safe to eat. But we can not cook the fish even though fish and chips on a Saturday night is yummy...wait what am I going on about????
Basically in cold temperatures the Koi are at less risk from getting infected by bacteria or parasites as it stops growing or slows down dramatically. Plus the Koi is quite a hardy fish and can with stand winter months.
I have mentioned it many times before that we all know that Koi produce huge amounts of waste which can become very harmful. But as the temperature drops the Koi slow down, they require less food if any which means less waste which means less toxic waste. Whenever having a pond keeping it deeper than 50cm will stop the pond freezing all the way to the bottom unless you live in Iceland...No not the Supermarket!!!
If you do have a small pond then please try to keep it not from freezing completely over, this helps stop the build up of CO2.
A pond heater will do this or what I did in my first pond at 13 years old was to have about 4 small plastic balls floating around. The water would freeze around the ball which could easily and carefully be removed to leave a nice unfrozen hole.
Also Koi keepers that are against heaters believe that they need to go through a winter period which helps them in their cycle of life and prepares them biologically for breeding season.
Summary of having a Koi Pond Heater
Having a heater in your pond helps provide all year viewing, but more maintenance.
No heater gives you time to rest and plan for the year ahead but you are in danger of disease from winter to spring.
No heater is cheaper.
My own personnel opinion is not to have a heater. I feel it is more natural not only for your Koi but for all other wildlife and plants as well. And with the money saved you can afford to have those fish and chips on a Saturday night.
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