Why is aquarium water green

Fish tanks turn green with algae, which needs light, water and nutrients to grow. Algae spores are airborne, so even if you start off with brand new everything, coldwater, tropical or marine, your tank will go green.

Algae are tiny plant-like dots that can stick to surfaces like the tank glass or even be free-floating in the water. A little algae is natural in any tank — some fish, snails and shrimp are even adapted to eat it, but too much algae is often a sign that there is an excess of light or an imbalance in the tank.

It can make the tank look horrible too and persistent algae problems can even cause some fishkeepers to pack up their nets and leave the hobby altogether. If you have live plants or corals they need bright light for a fixed photoperiod per day. I am always intrigued by the problem of green water in aquariums because the conditions under which it occurs seem to vary so widely.

Green water is the result of a bloom of unicellular algae, and is basically the result of two existing conditions — the fish aquarium is receiving too much light and the water has a high concentration of phosphates. Both of these conditions are necessary for algae, and neither alone is sufficient. As you have discovered, water changes are not solving the problem in your goldfish aquarium. Many tap water supplies these days have high concentrations of phosphates.

And, some municipal water sources have higher levels of nitrates than are found in established aquariums with biological filtration. Under these circumstances, water changes add, not reduce, the nutrients that support algal growth. There are several strategies you can use to eliminate green water. The first is to try reducing the light reaching the aquarium. Even if your aquarium is not in direct sunlight, the fluorescent light over the aquarium may provide enough energy to support algae.

If you leave the light off completely, the aquarium may clear in a few days. Then, you can gradually increase the light duration until the water starts to become green again. Develop and improve products. List of Partners vendors. Warning The water aggregators sold in pet stores that profess to clump suspended algae and remove it are not effective against green water. Featured Video. Article Sources. The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles.

Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Read More. Your Privacy Rights. To change or withdraw your consent choices for TheSprucePets. We will only use once in awhile and still clean and maintain on a regular basis. I completely agree with you that Acurel is an amazing product. I fall into the camp that prefers to avoid adding chemicals to water where possible.

Clarifier in particular can irritate sensitive fish. Regardless, I am happy that you found a quick and effective solution and thank you so much for sharing your experience! Thank you for this article! I also used acurel and no help at all what would you recommend doing? Can change the whole entire water and gravel in the tank while the fish is put into something else?

Same recommendations I make in my article. I give them a small wafer once a day. However, I have an aquarium background picture that I would think would reduce the sunlight.

Could the sunlight still be effecting the tank? Finally, do you suggest using the uv sterilizer, polishing pad, and daphnia together at one time?

There is also only so much algae an algae eater can eat. A UV sterilizer and polishing pad is just fine, combined with water changes. Most people just use a UV sterlizer water changes to great success.

Please Help!! I have a ten gallon tank that has a small goldfish, tetra, and a algae eater. The water turns green only one day after changing water completely which I know is not recommended but my only option with how bad my tank gets.

I keep tank covered all day long and only turn lights on at night when my son goes to bed. In the morning it gets recovered. I feed once every two days and have aqua tech filter rated for 10 gallons.

I have tried tetra algae control with no success at all. I really dont have any money to spend on uv filters right now but I also do see how that could even be the problem since it never gets sunlight anyway. I am at such a loss on this aquarium. Any advice is appreciated. As always, you should start by testing your water with an aquarium test kit. Hi, I have an outdoor fish tank with glass to the front and open to the top. Only goldfish but great! I have a uv steriliser and the water is chrystal clear.

The problem is that the glass and rocks and plants go slimy dark green in under a week! I have a large water pump too with a filter sending even more air bubbles cascading. Th water gets very warm, but I cover the top with white material to deflect sunlight but everything inside has to be taken out weekly and scrubbed clean.

How can I stop this please? Any ideas? I have other algae guides on the site, perhaps you can match it to one of those? My problem is green water. My light is on for no more than 10 hrs and I feed them every second day.

What could be causing the green water and how can I get rid of it please? Green water is not always a catastrophe. I had it in my garden pond, and it feeds perfectly my fry, my shrimps and my snails. You make a good point. Many fishkeepers use this to feed fry baby fish as well.

I totally agree with you , You can culture this as it is live diet for fish fry and also stimulate breeding. We have a new approx 2 mo old 20 gal tank that we think is still cycling.

How do you use a uv sterilizer as part of a healthy tank with an established biological filter? At 2 months, your tank probably should be very close to cycling, if it is. Once there is bacteria established in your filter, it will multiply there. I currently have a 37 gallon tank that is about 2 months old cycling and it is really green. Do I need to wait for the cycling to be finished or can I use the uv sterilizer or the pads right now?

It depends show far along the cycle you are. However, if you are just starting the cycle, then it can slow it down.

Hello Ian. I took my three garden goldfishes indoors for the winter here in Sweden. Bougth a 50l tank, came with led light and pump. The water is local, untreated groundwater. In two days it becomes really green.. I tried using rainwater too, and the same happens, tho in about a week. What to do? Groundwater can contain all sorts of different minerals and nutrients that algae uses to eat. I would recommend buying a test kit you should already be using one for ammonia, nitrite and nitrate for GH and KH.

Rainwater is not recommended as it is incredibly soft and can interfere with fishes ability to osmoregulate, which can stress and kill fish. Hello, I own a 2 foot wide tank with 5 Comet Fishes. The Comet Fish look healthy and eat well but even tho we change our tank regularly, water still becomes murky. We feed them pellets every night and btw the tank is outside, but sunlight doesnt really sine on it too often so i dont know what to do.

Block all sunlight, get a lid and performing regular maintenance should fix the issue. I have 10 gallon glow fish tank. It was ok for a long tim. I clean it every other week.

Changed water, added conditioner and defogger. Nothing working. They were fine up until about 4 months ago. The water is cloudy and the green algae is settling on the glass and filter again from last week I changed the water scrubbed all the pebbles cleaned out all the filters and glass. Put my filter care in and clean water treatment and its started to go cloudy and the green is settling again in the glass and filters.

I dont have plants in mine as someone said it could be those causing it. They are not in direct sunlight. Just normal daylight. I dont really have anywhere dark to put them. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. Sign up with your email for our newsletter and be notified when we publish new blog posts. Close Menu Blog. Aquarium thermometer.

Automatic fish feeder. Water changer.