Are Koi Ponds Cruel?

There are many debates whether keeping animals in zoos, using them for shows, even having them as pets is cruel to them.

Starting The Koi Hobby: A Step By Step Guide…

Regardless of how well they are taken care of, the animals are far from their natural environment and way of life. To some people, keeping them captive for the entertainment industry is as cruel as it can be. Some animals are even born captive.  Koi ponds are no different. Fish are also animals, they just inhabit a different environment.  

Every enthusiast who is starting to build a pond or already has done so, has asked themselves at least once if koi ponds are cruel? No, koi ponds are not cruel. There is, however, ignorance and neglect. Cruelty and harm to animals come from inadequate care and lack of knowledge for what your animals need. It is the same with koi ponds – fish do not suffer from the fact that they are kept in a pond but from a poorly maintained pond. “

Amongst the most common reasons for cruel ponds are violence towards the fish, neglect; lack of cycling the tank; lack of enough aeration; dirt; unclean water; absence of necessary bacteria; overcrowding and many more. However, the pond itself does not harm koi fish in any way as long as all sanitary and aquatic conditions are met.


No, koi ponds are not cruel. Neglect and ignorance are cruel. Before you start building your pond, take the time to do research and make sure you are aware of everything necessary for you fish’s wellbeing. Below, you can see more in depth reasons for koi fish suffering that can eventually prove lethal.

First of all, always remember that a pond is an artificial water basin. There is no natural aeration and balance between the aquatic inhabitants. Shortly put, these decorative oases are circulation systems for controlling the waste and aeration. Therefore, unclean water can be cruelty number one for koi fish.

1. Unsanitary Water.

Pond water cleanliness is controlled by a filtration system. Their task is to keep the water free of waste. The more time passes, however, the more bacteria develops from the pond’s flora and fauna. Also, if you buy the fish as juveniles, they will grow eventually. In the end, all of this means more and more waste and the filtration system may not be able to cope with it anymore. Unsanitary water is actually one of the most common reasons for fish deaths in ponds and aquariums.

2. Overgrowth of Algae.

Letting the algae overgrow is similar to a lack of adequate sanitation. Algae can turn the water into a swamp. In winter and early spring, algae are usually not as aggressive but in summer it can quickly spread out of control. Once uncontrolled, the plant makes the water thick, green and full of bacteria, which eventually leads to poisoning of the fish and finally death.

3. Lack of Healthy Chemical Balance.

During the day, water plants create oxygen and at night they ‘exhale’ carbon dioxide. This causes the pond’s pH to decrease and affects the nutrition cycle as well. If you are planning to switch off an aeration system, it is better to do it during the day and for a short period of time. Just to mention briefly, the pH measures how acidic the water is. It is one of the most important vitals and can affect the water quality. Rainwater makes the pH drop as well as garden fertilizers and any chemicals used for gardening. And one tip here: if you are just starting out building a pond, go for higher walls, edges and drains to provide reliable protection!

Bear in mind that the good pond water quality depends on a number of substances – stable pH, water hardness, healthy amount of carbonates, lots of oxygen, nearly zero ammonia, nitrite and nitrate correct levels. To keep the chemicals at their right values, you need to change the water regularly and provide proper water filtration at all times! The absence of a healthy and balanced living environment is 100% lethal to the colorful koi fish!

4. Nutrition.

Sometimes fish owners show cruelty to their aquatic friends simply out of ignorance for what food to provide. Feed the koi with the best quality food and avoid fish junk food at all costs, no matter how cheap it seems! Bad food is like tormenting the fish – eventually it will lose coloration and health, and its life span will be dramatically reduced. Also, overfeeding is just as unhealthy – the koi becomes fat and disproportionate. This exposes them to higher risk of tumors and internal blockages.

Finally, to close this part of the article, bear in mind a couple of simple bullet points:

  • Ensure clean pond water!
  • Prevent the overgrowth of algae!
  • Provide healthy chemical balance!
  • Try to never switch off aeration systems!
  • Avoid the penetration of chemicals such as fertilizers!
  • Change the pond water regularly!
  • Feed your koi with the best food only!
  • Avoid overfeeding! “

Below, we are going to explore even more reasons why koi ponds may turn cruel!


Koi ponds are not cruel. This misunderstanding comes from the general belief that keeping animals as pets is cruel. However, it all comes down to proper care and providing a comfortable living environment. Cruelty comes from ignorance and negligence but not from the water basin itself. Here are a few more sources of ‘cruelty’:

1. Overcrowding.

2. Skipping Quarantine Period.

3. Leaving the Hose Running.

In the beginning most people imagine a pond overfilled with glittering fish, swimming energetically around! And there is nothing wrong with that. However, overcrowding can lead to health deterioration. Filtration can get overloaded. Also, if you buy lots of small fish, they will grow up and there may not be enough space in the pond for a healthy co-habitation.

Overcrowding and keeping adding fish can contaminate the rest. Adding a new koi into your pond, without first quarantining it, can introduce new parasites, bacterial infections or viral infections. Before adding a new koi, keep it in quarantine in a 100/200-gallon horse trough tank with a filter. The quarantine should last at least three weeks.

Speaking of water, if you leave the hose on all the time after changing the pond water, your fish will be killed. Tap water is full of chlorine and other harmful chemicals.


Contrary to popular belief, koi ponds are not cruel. Wrong maintenance is cruel. Here are a couple of additional common misconceptions – summarized and explained!

1. Koi ponds don’t need too much maintenance – regardless of all advice, tips, suggestions and details to consider, koi ponds do not require too much to be kept in shape. As long as all necessary elements in the construction are included – rocks, gravel, aquatic plants, filters, air pumps and bubblers.

2. Koi ponds themselves do not attract mosquitoes – insects are attracted to stagnant water and not by the pond installation itself.

3. Koi fish can be kept together with plants – it is a complete misunderstanding that koi and plants cannot co-habit. To the contrary: plants are a must for oxygen provision and enjoy symbiotic relationship.

4. Koi fish do survive winter – some pet owners wrongly believe that a pond will be cruel to their fish in winter and kill it. Koi are actually very resistant fish and survive low temperatures. All they need is a spacious pond for swimming, oxygen and a hole in the ice (if any) to allow natural gasses to escape.


To wrap it all up, koi ponds are not cruel. Ignorance, negligence, little research and failure to provide proper living conditions for the fish are cruel. Make sure you arrange clean water at all times; control algae growth; ensure healthy chemical balance; provide aeration; give the best food and avoid overfeeding. If you are just starting out, do not overcrowd you pond all at once. Fill it in with fish gradually and calculate how many gallons of water you will need for all fish. Before adding new inhabitants, always quarantine them for at least three weeks in order to prevent possible contamination with parasites. Avoid believing in rumors that koi ponds are difficult to take care of and be brave. You can have a great koi pond, just do it right!

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