Occasionally we see clients with the issue of green spa water. Unlike pool water this is not caused by algae. For algae to grow it requires sunlight, so unless your spa has no cover on all day in the sun, this is likely not the cause of your green spa water, especially here in Canada.
If you have green tinted water your culprit is a high
mineral content of iron and/or copper. You may notice when you first fill your spa the your filter becomes covered in orange or brown color, after the first week or so of washing the filter it tends to ease up a little but as it eases up your water may gradually shows more of a green tint, especially after adding chlorine or bromine granules or a shock treatment. This is because the chlorine content of these products oxidizes or rusts the minerals in your water.
If you often experience green water due to high mineral content my recommendation is using a pre filter to fill your spa to reduce the amount of minerals you are introducing into your spa. After you've filled the spa using re filter using a mineral collecting tool or product such as the Dazzle Eliminator will collect minerals still present in water. A stain and scale product or Mineraluxe Cubes will protect your system while there is still a presence of minerals in the water. I also recommend rinsing the filter frequently in the first week following the refill to rinse away as much of the minerals on your filter as possible. This will help prevent them from "falling" back into the water.
If your source water has been tested by a professional and does not have a high mineral connect but as your spa water ages the mineral content increases, then you need to consider changing your water care products. Many manufactures of low grade products, often found in big box stores, contain many impurities. Often fillers and minerals that are not necessary or wanted in your spa water. If your water starts off with little to no mineral content and increases with time, this is the reason. Changing products for high grade with less impurities may cost you a little more to start but in long run will cost more since you'll have less correcting to do, less wear and tear on your spa components, and less abrasive to your skin.
Is green water a huge problem? No, but it still requires correcting to prevent damages to your spa components. And can make spa water look less appealing to bathe in.