Koi Health

Beautiful Koi fish come from the common carp, and have been bred to have such beautiful colors and patterns. The common carp is a tough fish and for the most part it can survive in very poor water conditions and host a serious parasite population without getting sick. But because our modern day koi have been selectively inbred to produce the beautiful colors and shape that we all love, they have lost much of their ability to endure such harsh treatment.

The good news is that even despite their inbreeding, Koi fish seldom get sick and die without a reason. I recently had one die and I was devastated. I needed to know the reason it died. I was also unsure if there was a bigger problem I had to tackle, and if other Koi in my pond would suffer the same fate. So naturally, I went to the books and did some research.

The common reasons Koi fish die are as follows:

1.      Poor water quality

2.      Parasites

3.      Ulcers and disease of their fins and skin

4.      Predators

5.      Lack of oxygen

6.      Medication overdose or water over treatment

7.      Jumping out of the water

8.      Viruses

9.      Toxic pesticides or chemical fertilizers

10.  Tumors

The first three are the main cause of poor health in 70% of the cases.

POOR WATER QUALITY

Like the air we breathe, water is of paramount importance to fish in general. Poor water quality can be lethal to a Koi, and it would not be a surprise to see all the Koi in the pond die overnight… Now that is what I call a nightmare!!!!

The most popular issues with water are low oxygen, and high ammonia, nitrite and nitrate levels.  There are commercial water kits that can and should be used regularly to test the quality of the water. Pumps and filters are all useful to maintain proper water quality.

PARASITES

Parasites are a kind of bug that can be given from one fish to another. The main cause of a parasite infection is when a new fish is introduced to the pond. Before a new fish is introduced to the pond, it should be quarantined, or set aside from all the other fish for at least 3 weeks. During this time period the Koi should be observed and treated for parasites. Always try to find out where your fish came from, and make sure the ‘dealer’ is open about their parasite policy, and treat their Koi for parasites and is parasite free before selling it. It is recommended that you do not take their word for it, but instead ask about their ways in treating parasites, and so forth. If they are not straightforward, assume that you need to treat your new Koi yourself.

BACTERIAL INFECTIONS

The two most common bacteria that cause problems on koi fish are Aeromonas and Pseudomonas.

These bacteria hate chlorine and thus are not present in tap water, but on the other hand, both Aeromonas and Pseudomonas are common inhabitants of ponds. They live naturally in pond water. If you add tap water to your pond, the chlorine in it is usually treated as it can be toxic for the Koi, and chlorine usually evaporates within a couple of days. It is no surprise that your pond would have these bacteria. Normally, in a clean healthy pond, the levels are very low, and the slimy coat that covers the fish protects them from the bacteria.

Bacteria become a problem when the slime coat that covers the fins – skin of the fish is broken and the bacteria then have access to cause infection. For this reason it is important to monitor your Koi’s movements, skin and general appearance. Bacteria can grow very easily if not treated right away.

 I hope you will find this helpful when considering Koi Health.

Margarita Ochoa-Maya, MD