
What is it?
The green in the water is caused by microscopical green algae called phytoplankton. You will notice them when millions of these phytoplankton get together to form a large group. When low in number, these phytoplankton will turn your aquarium a slight hazy-greenish color and as they increase in number so will the unsightly greenish brownish soupy mess thicken in your aquarium.
Will the green water harm my fish?
What causes it?
- Too much light
- Stagnant water
- Nutrient imbalance
- Unmaintained aquarium
How do you get rid of the green water?
- Reduce light
Shut the aquarium lights off until the water clarity is back to normal. With the lights off the water clarity will improve way quicker. I know you love to see your fish under lighting but trust me it will be worth the wait.
- Increase water movement
You won’t see this advice in other articles, but trust me it works. Add a wavemaker or even a cheap air stone. Anything that will add more water turbulence. The extra water movement plus the added oxygen that will be absorbed into the water will break up and starve the groups of phytoplankton and get rid of the unsightly green water.
- Ultra Violet Sterilizer
Install an Ultraviolet (UV) filter. This will kill algae cells that pass through the UV light. You don’t need a high wattage UV for this. Depending on the size of your aquarium even a relatively inexpensive In-Tank UV sterilizer as low as 9watts can do the trick.
- Chemical Removal
As a last resort use one of the aquarium algaecides on the market and make sure to follow directions and not overdose. I say as a last resort because I hate adding foreign chemicals to my body and I hate adding them to my aquariums. Besides, they usually are only a temporary fix.
Conclusion:
Experiencing a free-floating algae bloom is not a cause for panic. The fish are not in immediate danger. But you definitely want to get it remedied and under control. Getting your algae problem under control may be very quick, or it may take some time. When experiencing a free-floating algae bloom, it may take several water changes to get the green discoloration completely out of the water. But only do this once you have the cause of the algae growth under control. Follow the suggestions above and you and your aquarium will be fine and as a side benefit your aquatic environment will be the better for it!
Are you still having issues after following the above-mentioned advise? feel free to contact us with any questions or experience you had dealing with this issue.
About the Author

Sol Bick
Aqua Creations Founder
Aqua Creations founder and self-proclaimed fish addict, Sol Bick is passionate about anything aquatic. With over 50 years of experience as an aquarium hobbyist and professional, Sol never stops plunging into the depths of aquatic science, researching, contributing to, and staying current with the latest technologies.