During the last five years I had no problems with my pond. This year however, the Koi flash and are lethargic, just lying at the bottom. I went to a Koi dealer, and he gave me Malachite green to treat, but I do not see any changes. Is Malachite green the right treatment? I also have green algae on the sides of my pond which I never had before. What is the problem?

Phillip wrote:

During the last five years I had no problems with my pond. This year however, the Koi flash and are lethargic, just lying at the bottom. I went to a Koi dealer, and he gave me Malachite green to treat, but I do not see any changes. Is Malachite green the right treatment? I also have green algae on the sides of my pond which I never had before. What is the problem?

Hi Phillip, this is the typical problem of koi keepers this time of the year. September and October are the most difficult time in which most deaths occur. This is mainly because your koi are getting active and eat like crazy, but your biofilter has not kicked in after the winter. Nitrosomonas and Nitrobacter takes awhile to develop again after the winter. That is why it is essential to limit their food intake until the biofilters kicks in, especially if you are a bit over stock.

It is quite clear that you have a parasite infection but you must first establish what the primary cause is, before you treat the secondary reaction.

1. Get yourself a pond test kit. The possibility that your nitrites are too high is very good. If so, you are overstock or you gave to much food at a time when your biofilter has not kicked in. Maintain a stocking level of 666 cm per 10 000 liters.
2. If the nitrites are very high, do an immediate 30% water change and add 4 kg of salt per 1000 liters, which combats the effect of the poisonous nitrites and will kill 80% of parasites and will help to prevent a further secondary problem of a bacterial infection.
3. Stop feeding.
4. Now you have to treat your parasite problem, but the shotgun approach of a Malachite treatment is not good. You have to know what you are treating for. Malachite green would treat for almost 80% of parasites, but what if it is fluke, and the possibility is very high because you said that the Malachite green did not have a good effect. The Malachite green will not kill fluke and some other parasites, and the fact that you have already treated with Malachite green, excludes you now from treating with other medication immediately and Malachite and a high concentration of salt does not go together. Bottom line, you should either get yourself a microscope to check which parasites are present, or you will have to get an expert in to do the scraping for you, so that you can treat for the specific parasite present.
5. If it is costia or white spot for instance, you can carry on with Malachite green. If it is fluke, you should get rid of the Malachite green over a period of three days and treat with Potassium Permanganate or other effective fluke treatment.
6. Carry on with water changes every few days until you see that the nitrites have dropped to zero and do regular ammonia and nitrite tests until you are certain that everything is fine again. They will need time to recoup after the treatments, and perfect water conditions are now of the utmost importance to prevent a bacterial infection which very often kicks in after a parasite treatment. Maintain a high level (4kg / 1000 l) of salt for a while.

With reference to you blanket weed problem, in view of the fact that your pond is already matured ( or should be after five years), you probably did a very big water change which caused the blanket weed, alternatively you had a lot of rain in your area which adds nutrients to the water and cause an algae bloom. The 4kg of salt mentioned above and a bit of patience should sort out the problem, alternatively, go to "water conditions/green water" on my web site. http://www.koionline.co.za , Rgds, Paul