Green Water in Aquarium – Causes & How to Fix it

Most of us experienced something like this before. All is very much fine inside your aquarium. The water is translucent, your fishes are swimming around cheerfully, and everything’s in order. Until one day, your gorgeous fish tank has transformed into an unsightly debacle, seemingly out from nowhere.

The water is a striking greenish tint, and then you can scarcely see inside. You rush through massive water changing and replace the cylinder for your filtration system. Things got better after a day or so, but then everything shifted back again. Perhaps, even worse.

In most cases, this is what fish tank owners refer to as Green Water in Aquarium. What really is this, and what can you do about it? Read more to know.

What is Green Water in an Aquarium?

Green Water is an outburst inside a fish tank produced by a rapidly growing population of stranded algae called phytoplankton. The name algae refers to a wide and varied collection of photosynthetic cells of eukaryotes.

Green algae, unlike other algae plants that generally grow on the surface or structures of your tank. It hovers around the aquarium and proliferates countless times in a short period.

The unappealing green water, which occurs inside the tank occasionally, is commonly referred to by aquarists as algae bloom. Algae, like other plants, obtain energy and develop by photosynthesizing sunlight. Freshwater green algae are perhaps the most common type of algae seen in aquariums.

Algae is inherent in aquariums, and it may offer food for mollusks or other aquatic animals inside your tank. The issue arises whenever the bloom becomes out of hand, turning the environment in your tank cloudy and hazy.

The green appearance is the effect of an increased density of the microscopic algae, which decreases the clarity of the water. In extreme situations, the water would be tremendously green that even the fish couldn’t be seen. ​

Causes of Green Water in a Fish Tank

Green water is commonly from an overabundance or lack of several factors inside your fish tank, like imbalances, sunlight issues, or inadequate methods in taking care of the fish tank. To know more about this, here are the prevalent causes of it.

Imbalance in Nutrients

There’s just too much fish, leading to higher waste materials, which offer nourishment to algae. Aquatic plants, including algae, benefit from fish excrement fertilization.

Plants, of course, require nutrients to grow. Like most algae, this implies nitrates and phosphates, which are generally found in aquaculture feeds and manure but can also be found in tap water.

Excessive feeding or keeping a substantial number of fish without considering your aquarium size or filtration system capacity contributes to nutrient imbalance. A similar effect may be obtained by doing water changes using nutrient-rich tap water.

Inadequate Maintenance Practices

Water quality gradually deteriorates due to a lack of periodic water change and adequate maintenance. This poor habit provides extensive habitat for algae to develop over time.

Because we can’t detect micronutrients, no one indicates how awful circumstances are unless something unpleasant happens, such as our fishes being unwell or algal bloom.

Excessive Lighting

Algae, like all plants, requires three things to survive: light, water, and nutrients. Too much light, particularly direct sunlight, seems to stimulate a plant to be healthy and flourish. If either of these elements is in excess, algae may spread quickly, like weeds in a garden.

Algae blooms are more prevalent in aquariums that are exposed to direct sun. Excessive light may be caused by putting your fish tank in a bright room, letting the tank on full exposure for an extended time, or even a light that would be too intense for your aquarium.

Is Green Water Dangerous for My Aquarium Fish?

Green water is usually not dangerous to your fishes, any aquarium inhabitants, even to you. However, it’s unpleasant and, in extreme situations, can hinder the passing of light through your fish tank plants. Surprisingly, some phytoplankton is advantageous.

Some seawater marine enthusiasts produce or buy cultured phytoplankton, particularly to administer as food for their corals. At the same time, freshwater keepers raise phytoplankton called infusoria to serve as food to specific species. However, for most fishkeepers, these algae should be avoided or removed.

How to fix Green Water in a Fish Tank

On the day that you found the emerging green water in your fish tank, here are some solutions that you can apply.

Installing an Ultraviolet Sterilizer

Installing an ultraviolet (UV) sterilizer inside your fish tank is by far the most effective and convenient approach to get ahold of green water. As water travels via the UV chamber, floating algae will also be destroyed, including numerous harmful organisms.

In a few days, you’ll have pristine water. UV sterilizers are entirely safe for fishes, animals, and plants. Plus, it has recently become more inexpensive and simple to install.

Having a UV sterilizer inside your fish tank, you wouldn’t worry about green water again.

Treatment using Chemical

There are several treatments available that help removes green water blooms of algae. However, it is crucial to recognize that chemicals might have negative consequences.

In reality, chemicals don’t really treat the underlying source of the issue, and you can’t be certain of their implications on your fish, aquatic plants, or even the aquarium’s environment. Having said all that, they may work across many situations.

Using a Water Polishing Pad

The phytoplankton, which makes your water greenish, is so tiny that your filtration system can’t capture it. These organisms keep sneaking in. Thankfully, a modest tweak may transform your filtration system into something like an algae-capturing device by using a polishing pad.

The polishing pad can remove even the smallest particles inside your fish tank, offering you gleaming clean water.

As you would expect, this renders a polishing pad ideal for eliminating the greenish tint off your fish tank water.

Understand that your filtration system needs replacement as it captures and eliminates algae from the aquarium, so have a spare available and switch it out when it clogs.

Total Elimination of Light for Days

Excessive light is frequently a catalyst for green water. One method for eradicating such an incident is to turn off the lights for a while. Switch off your aquarium light and wrap the aquarium with a pitch-black cover for a few days — garbage bags or any cloth will do.

Remove the aquarium cover for a few minutes every day when feeding your fishes, then cover it again. Across many situations, the algal bloom may fade off after a few days.

However, the source of the bloom must still be addressed. You should try a different approach when you do not notice improvements within the next two to three days.

Put in Daphnia (Water Flea)

It would be better if another organism is doing the job of getting rid of the green water for you. If you would agree, then it’s high time to have water fleas known as daphnia.

This little critter will gladly consume the algae that turn your water greenish. You may buy them alive locally or on an online fish store. Often in the threatening green water, a hundred daphnias may swiftly create a difference. It is indeed natural, inexpensive, and efficient.

Your fishes will also appreciate the addition of daphnia to your fish tank. Daphnia is a favorite food of several fish, including tetra and betta.

It is critical that you accurately determine the green water in your aquarium is caused by phytoplankton rather than any other type of alga. Other forms of algae are not edible for daphnia.

How to prevent Green Water in a Fish Tank

Determining how to treat algae buildup is only the first part of the solution. Working on preventing or resolving an algae proliferation problem would be next.

Decrease the Lighting

Avoid setting the tank in direct sun for extended exposure. Algae bloom may and would be aided by sunlight. Whenever utilizing led lighting, ensure it isn’t too bright and that it isn’t on for over 8 to 10 hours every day. Utilize a stopwatch to switch the artificial lighting on and off throughout the day.

Examine the Tank Water

Examine your tank water for nitrates and phosphates regularly and take action if the levels become too high. Tap water may potentially contain substantial contents of phosphates and nitrates. Therefore, check these before putting them in the aquarium.

Have Living Plants

Most of those nutrients, which algae require, will be absorbed by living plants. When there are fewer nutrients and minerals in the aquarium water, fewer supplements for algae development will be eliminated.

Adequate Dosage of Plant Fertilizers

When it comes to aquatic plant fertilizers, steer clear of less rather than more, specifically when you don’t utilize carbon dioxide or have a small number of plants. Consider that algae are like plants, so they will consume any surplus nutrients that your aquarium plants aren’t absorbing.

Additionally, please note that a fish tank can never store more water than its stated capacity. A 20-gallon fish tank, for example, generally holds around 16 gallons of water once stones, pebbles, and other accessories are added. Measure as needed.

Plan Maintenance Regularly

Changing water regularly is a crucial step for keeping an aquarium fresh and eliminating algal blooms. Weekly you can change 10 percent of the water, 25 percent every two weeks, or anything feasible for you.

Change hang-on filtering cartridges monthly, and maintain cylinder filtration on a routine basis. Clear or change hydraulic filtration every four to eight weeks and replace activated charcoal or any other biochemical material.

But, if you had recently arranged your aquarium or a cultivated tank that requires bottom fertilization, skip cleaning the pebbles. Remove any food scraps and some other organic debris, then suction the pebbles softly. Ensure that the new water is clear from phosphates and nitrates.

Conclusion – Green Water in Aquarium

Some people may prefer green water in the aquarium. However, remember that green water is an unwelcome intrusion that obstructs our vision. Therefore, it’s preferable to take it away.

Green water must no longer be the case in your fish tank now since you know what it really is, what develops it, as well as how to prevent it.

Just like with any aquarium concern, one of the preventative strategies is to maintain the aquarium clean and make frequent water changes.

Keep in mind that an immediate response to rapid algae development may help you avoid potentially serious issues in your aquarium.


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