What is Green Water (algae boom)?
It is one of the most common algae problems, where some hope to achieve and some hope to alleviate. Usually, this occurs in newly started aquariums, as the problem occurs from several factors: high nitrates, phosphates, ammonia/ammonium and lights. Further, it’s possible that the water does not appear green, but very foggy at first. The colour will depend on the amount of free floating algae is in the tank, along with the bacteria bloom. It is important to remember that this is not usually one type of algae that inhabits the water. There is a myriad of different types of microorganism that also contain chlorophyll in their structure living in the green water. While, ammonia/ammonium in the water with high phosphates is likely to be consumed quickly by the algae, the microorganisms switch to nitrates and continue to exist in the water.
This does mean that Green Water is not detrimental to fish or invertebrates in this stage. High lights are usually a major factor in green water. It is very unlikely to have green water in a low light aquarium, as there is not sufficient amount of photosynthic energy for free floating green algae. There are detriments to the green algae beyond the unsightly appearance of your aquarium. This includes blocking light from penetrating through the water for your aquatic plants. This could cause a massive die off of plants, affecting your aquarium’s balance with the nitrogen cycle. With an increase of ammonia, nitrites and nitrates, green water at this point is a major problem.
Uses of green water?
Green water is not necessarily bad. Many fish fry and invertebrates love to eat the microorganisms in the green water. It is a source of great nutrients that is necessary for their growth. Invertebrates like Fan Shrimp aka bamboo shrimp thrive in an aquarium where there is a healthy supply of these floating algae in the water. Likewise, freshwater clams also require these algae in the aquarium. The ability to cultivate green water is necessary for keeping fresh water clams. When trying to cultivate green algae for your aquarium, there is multiple ways of doing it. The easiest way is to put plant matter, or any matter containing high chlorophyll into a jar filled with tank water and let it decompose in sunlight. The chlorophyll and nutrients will be released into the water, and fed to microorganisms that will quickly multiply. This can then be used to feed your water. It’s very important to control the amount of green water you put into your tank when feeding. Cultivating green water out of your tank is considered a better method than cultivating it in your tank, as it keeps your tank water clear.
Clearing Green Water
There are a few methods of clearing green water. The first step to these methods is to perform a water change. While this does not permanently clear the water, it will do so temporarily. After this, perform a black out period, in which you block out all light completely for 3 days or more. Remember to cover your aquarium with a blanket to ensure no light gets through.
This method may not work, if your aquarium is planted and have high light needing plants.
Introduction of daphnia could help defeat green algae, as they love these microalgae. In an aquarium with fish, they will be quickly consumed in return. However, remember that your fish may finish eating the daphnia before they finish consuming the green water. In an invertebrate tank, you will be stuck with the daphnia.
UV sterilizer will also kill free floating algae. They will also kill parasites and bacteria in the water. The downside of a UV sterilizer is that they are expensive and in extended use will cause a deficient of certain nutrients needed by plants. Depending on the amount of green algae in the aquarium, they can also be clogged quickly.
Similarly, a diatomic filtration is another method for eliminating the green water without stressing your fish or invertebrates.
Personally, I've used a fine sponge filter powered by an air stone for an hour to eliminate green water in a 10 gallon tank, followed with a short black out period. Hydro-sponge filter was one of the few sponge filters I found capable of doing this. Just remember to rinse them afterwards.
While there are chemical methods for removing green water algae, it is often with caution that I recommend them. The chemicals are usually harmful to invertebrates and fish. There have been stories that fungus medication for freshwater fish by Jungle have cleared green water.
Preventing Green Water
Prevent green algae from forming by reducing the essential nutrients needed for it to form. You can do this by performing regular water changes. Ensure the water being used is not high in nitrates or phosphates. Also, perform regular gravel siphoning to clean the aquarium substrate. Remember to do this in parts, as stirring up the substrate can cause bacteria and algae blooms. Furthermore, control the amount of lighting, and avoid direct sunlight on the aquarium. Lastly, avoid overfeeding or overstocking the tank, what goes in one way does come out the other.
