1. Constructing a koi pond without proper filtration.“Take care of the water and the water will take care of the koi,” is a popular saying. Another expression popular among hobbyists is, “We don’t keep fish; we keep water.”

Our experts remind us that koi are living creatures with an immune system that works to keep them healthy. In good water, their immune systems will usually be fairly successful at doing so.

2. Overstocking a pond. Too often, first time hobbyists will put too many koi in their pond without considering the capacity of the installed filter. This will cause an imbalance and may result in stress or even death for the koi.

3. The wrong diet. Edward warns that too much animal protein and oil―like what koi absorb when they are fed cat or dog food―is bad and may affect the liver and other internal organs.

This story appeared in Animal Scene’s April 2015 issue.