Why Is My Aquarium Water Green?

Why Is My Aquarium Water Green

If you have an aquarium, or know someone who does, chances are you have seen that, sometimes, the water looks green.

It can be super concerning and jarring to see, especially if you haven’t seen it before.

So, if this is a problem that you have or are currently experiencing and want to know how about it, you have come to the right place.

What Makes The Aquarium Water Turn Green?

To understand a little more about the green water, we need to know what makes it turn green?

Basically, the reason your aquarium water is turning green is because of algae.

These tiny bits of algae grow because of a surplus of nutrients and light in the fish tank.

The surplus of nutrients comes from the nutrients building up in the water.

When algae has too much light or a large amount of nutrients, it will grow very quickly.

Phytoplankton, which are made of single-celled algae and cyanobacteria, are the living parts in the tank and part of the algae.

These organisms can only be seen under a microscope but play an important part in nature.

When there are too many phytoplanktons, however, they will become too concentrated and turn the water in your fish talk green.

This is called ‘algae bloom’ and is a very common occurrence and nothing to worry too much about initially.

If it is left for too long, though, the aquarium water can become thick and turn a yellow-green color.

With that being said, the three main reasons for your aquarium water to turn green are as follows:

  • The nutrients in the tank are out of balance (too much or too little)
  • Too much light in the tank
  • You aren’t maintaining your tank properly

To give you a better understanding of these three issues, we will look at them in further detail and learn how to overcome these problems

The Nutrients In The Tank Are Out of Balance

The combination of fish waste and food creates the perfect nutrients for algae to grow.

The nitrate and phosphate that gets excreted into the tank by one means or another give algae everything they need to not only grow, but thrive.

If you have too many fish in your tank, or over feed your fish, nutrients will build up.

If your tank or filter is not big enough to handle the number of fish you have, you will experience this green, sludgy water in no time.

You will also have this problem if you use nutrient-rich tap water when you are doing the water changes for your tank.

Too Much Light In The Tank

Since light is an important ingredient needed for algae to grow, too much of it can have detrimental effects on the condition of the aquarium.

When there is an overload of light and nutrients, algae goes into overdrive and can take over your tank in a very short space of time.

If you are using a light that is too strong for the aquarium you are using, algae will flourish.

Likewise, if your aquarium is placed by a window that gets a lot of sun or if the light is left on for too long, you will get the same problem.

You Aren’t Maintaining Your Tank Properly

Aquarium hygiene is a huge factor when it comes to algae bloom, too.

If you are not changing the water frequently enough, the condition of the water will deteriorate as more algae is created.

This is a difficult point to understand since we as humans cannot see the nutrients in the water.

We only find out about them when we see algae bloom or the fish get sick or worse.

Preventing The Water In Your Aquarium From Turning Green

There are loads of things we can do to prevent your aquarium water from turning green.

If you want to find out what you can do, keep reading to learn about some helpful tips.

Do Not Feed Your Fish Too Much or Too Often

You should only have one inch of adult fish per net gallon of water in your tank.

When you are feeding your fish, they should only have enough so that they can consume it all within two minutes or less.

You should only feed your fish once or twice a day.

Preventing The Water In Your Aquarium From Turning Green

Many people will say that you should skip one day of feeding per week.

Doing this will ensure that any leftover food in the tank is consumed, reducing the nutrients that algae can use in the tank.

General Maintenance Habits

You should regularly change the water in your aquarium to keep the environment healthy.

If you siphon 10% of the tank every week, or 25% bi-weekly, you should be able to keep on top of the algae.

All organic material and uneaten food should be removed, and the gravel can be slightly vacuumed (unless your aquarium has just been set up, or you are using a tank with substrate fertilizers).

The water you add to the tank needs to be free of phosphate and nitrate, or else you won’t be doing anything beneficial.

The hang-on filter cartridges should be replaced monthly.

Additionally, the service canisters must be refilled regularly and the mechanical filter media needs to be either rinsed or replaced every 4 to 6 weeks.

The same timeframe should be sued when changing the activated carbon / chemical media.

Be Mindful Of The Number Of Fish In Your Tank

This tip is pretty straightforward – if you have too many fish in your aquarium, their excrement and food will cause a buildup of nutrients in the tank.

These nutrients are what algae thrive on, so you will be giving the unwanted visitor exactly what they are looking for.

Choose The Correct Lighting For Your Tank

Don’t place your aquarium in a place that gets too much light, like a sunny window.

If you’re limited on space, get a background material or draw the shades to limit the excess sunlight.

If, however, your aquarium sits in a bright room with no direct sunlight, make sure to keep the tank light off in the daylight hours.

You also need to pick a light that fits your aquarium correctly.

To do this, you need to take the depth and size of the tank into account.

Choose The Correct Lighting For Your Tank

You can install a timer, so you can control the hours of light the aquarium gets and create a day/night cycle for the fish.

If you have plants in your tank, you will need less light.

Generally speaking, aquariums with plants require between 8 and 12 hours of light every day, while tanks without plants only need 6 or less.

Test Your Water Frequently

To keep an eye on the nitrate and phosphorous levels in your tank, you will need to test it regularly. Before using tap water, you should test that, too.

Tap water is often rich in these nutrients and will not be good for use in your aquarium.

Instead of using tap water, you can use deionized or reverse osmosis water.

You can add water renewals to the water, too.

Use Live Plants

Because algae and aquatic plants need the same nutrients to thrive, planting live plants is a great way to reduce outbreaks of green water.

Other plants that float like hornwort or duckweed are also effective ways to reduce algae bloom.

This is because they reduce the amount of light that penetrates the aquarium’s deeper water.

It is very rare for aquariums with live plants to ever have problems with algae, so using them is definitely something to consider if you aren’t already.

Curing Your Outbreaks Of Green Water

Chemical Treatments

Chemical treatments should always be your last resort when it comes to battling algae in your aquarium.

They often have adverse effects on the fish and plants in the tank, so all other options should be exhausted before moving onto this method.

Diatom Filter

Despite their price tag and, these filters trap microscopic particles.

By them trapping the particles, your water stays beautifully clear.

Eliminate the Light

You can eliminate all light for up to 72 hours to get rid of algae blooms.

This, however, may not work every time and the time should never be extended for longer than 72 hours.

Use A UV Sterilizer

This is probably the easiest way to get rid of algae bloom and green water.

The ultraviolet sterilizer eliminates algae as well as organisms that could potentially cause disease.

Final Thoughts

Now that you know what causes your aquarium water to turn green and how to fix it, you shouldn’t have any more problems on the matter.

While there are always ways to undo the damage of green water, prevention is always better than cure.

So, if you want to prevent green water from being an issue in the first place, the best option is to either get live plants, a diatom filter or a UV sterilizer.

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