Typical koi pond

Having a Koi pond can not only increase the visual appeal of a property, but it can also aid in developing a passion for an environment that you are able to maintain for yourself.  Koi ponds can certainly encounter a number of issues throughout time, especially considering the amount of time and effort that one puts into maintenance, but this does not mean that such problems cannot be solved and alleviated with a few simple suggestions.  The following will outline 5 of the most common problems associated with Koi ponds, as well as ways in which such problems can be solved.

1. Water Quality

This is THE leading cause of the death of Koi fish.  It largely stems from the fish’s waste products and the first iteration of that is ammonia. Unfortunately, many people do not realize that they are having this issue until the koi’s gills are burned by the ammonia.  

You can use chemicals in the short term that sequester the ammonia but ultimately you really want to address your filtration and levels of beneficial bacteria.

In the biological cycle of a koi pond ammonia is produced from fish waste, which gets turned into nitrites, then nitrates.  Its important to become familiar with the basics of this process to understand better how to treat and prevent water quality issues.  This article and graphic describe this process in more detail. 

Really high or low pH’s can also contribute to the death of fish.  Koi ponds may have a pH range between 6.8 to 8.2 but 7.0 to 7.5 is really ideal.  There will most likely be natural daily swings of pH of a small amount but that is not something to be concerned about as long as they are small. 

The concern becomes big swings in a short time or generally pH levels that are outside the acceptable range causing koi skin to become vulnerable to bacterial infection.  Two main solutions to keeping pH levels in check are regular testing and if need be adjustments via buffers and acids.  In short, buffers will increase pH while the addition of acids will reduce pH.

2. Diseases

Parasites on or in your fish can not only be difficult to identify, but they can be nearly impossible to identify as many are too small for them to be seen by the naked eye.  

Bacteria are everywhere in nature, including your koi pond.  There are good bacteria and not-so-good bacteria.  If your fish are stressed for any reason that can increase their vulnerability to bacterial infections (especially if they have a lesion or injury).

Water quality is at the heart of disease prevention so although you can treat diseases as they arise you will be doing yourself and your fish a favor by getting your water chemistry right.  

If you are experiencing an issue of this nature, then consider a better filtration system such as one that incorporates a UV sterilizer. For more on koi diseases see this article.

3. Algae Growth

If you find that your Koi pond has excessive algal growth, which can decrease your ability to see your fish, then there are several ways to manage the algae in your pond. 

You can choose to either tint the pond water, which will reduce the ability of the algae to gather sunlight, or you can add just a slight amount of salt in the pond, but only if you do not have other plants growing that don’t have some salt tolerance.  

At the heart of algae problems is water quality/chemistry.  If you can remove one or more of the elements that allow algae to thrive you will come out on top.  

Algae Box-what algae needs to grow

4. Overcrowding

When it comes to koi, less is more.  You don’t necessarily get more satisfaction out of 30 fish than you would with 10.  Keeping your population to a manageable level avoids lots of other potential problems like excessive waste build-up, depletion of dissolved oxygen, stress from crowded conditions leading to disease.

The more koi you have, the more koi you will have.  Koi breeding will really inflate your population size. Crowded conditions will cause a physiological response in koi that “tells” their bodies to reduce growth hormones resulting in smaller koi overall.

5. Predation

It can be a serious issue with koi ponds, especially during the overnight hours.  Cats, raccoons, wading birds, river otters and even larger coyotes have been known to prey on the fish in Koi ponds. 

If you are finding this to be an issue for you and your fish friends, then consider making the water too deep for large birds or animals to stand in or place netting on the surface of the water to pose as a barrier between the fish and the predator.

In conclusion, taking care of your koi and the pond they live in is a process but one that you can learn and get better at over time.  Its easy to get overwhelmed by what may appear to be complex but any large problem is merely many small problems that can be tackled one by one.  By addressing water quality first and spending the most time on mastering that, fish health and pond health will follow.