At some point in time every Koi pond will develop an algae problem. The important thing for the Koi keeper to understand is what a good algae is and what is a bad algae. No doubt many of you will be wondering, how there can be good algae in a pond. We will have a look at the causes of algae and how to prevent it.
The first thing to understand is that the fish in your pond excrete nitrogenous waste products and phosphates which stimulate the growth of Koi pond algae. This is more prevalent if there is a good deal of natural light and will be noticed by the water turning green. To an extent this is not necessarily bad for the pond or the fish as it helps to bind some of the harmful nitrogenous wastes and phosphates in the water as well as releasing large amounts of oxygen in the water during the day. However if it becomes out of control you certainly will not be able to enjoy your fish and the algae will begin to take in too much oxygen at night, resulting in a lack of oxygen for the fish.
If this does start to happen you will notice the fish being distressed in the early morning, gaping for air at the surface. The other problem is that the Koi pond algae will remove carbonic acid from the water during the daytime creating wide pH fluctuations between day and night. High pH levels during the day may interfere with ammonia excretion by the fish. In most cases however light green pond water is not harmful to the koi, unless of course if the pond is highly overstocked. The best treatment of green water is prevention; the best form of prevention is by installing a UV light. If at some point this fails make use of a mild algaecide which is easily available online or at your local Koi dealer.
Another major problem often found in Koi ponds is stringy algae. Stringy algae grow off the sides of the pond, by waterfalls, and off potted plants in the water. In general it is a sign of a healthy pond, meaning all the required nutrients are prevalent. The only problem with this hair like algae is that it can quickly take over and cover the pond. The easiest and best way of getting rid of stringy algae is by catching it early and lucky for the hobbyist Koi enjoy eating it! Simply put, stop feeding the fish for up to ten days and it should be clear, and do not leave it longer as the fish still need their extra nutrients. If the problem persists the only other real measure is manually removing as much as possible or by using strong algaecides. Remember to remove all plants from your pond when using strong algaecides.
Now then, the good algae are the lovely green algae that colonise the sides of the pond as well as any objects in the pond. It has a short hairy moss like look to it with a soft texture. Please do not start scraping it off, from the sides or use algaecides when it is not necessary. If it does bother you cease feeding your fish for a couple of days, and you will notice it disappears quickly.
Koi pond algae can be a pest, by taking precautionary measures and acting quickly you can prevent green water or excess growth of stringy algae. So remember be cautious, watch your pond that’s why you built it in the first place…