This harmless aquarium algae can make your aquarium water turn to intransparent green. So, it's called Green Water or Green Tank and quite difficult to eliminate.

This algae bloom is actually groups of high-density individual rounded algae. Causes of the algae bloom are too strong light and too much nutritions (ammonium, nitrate, phosphate, silicate and others).

Simply change the aquarium water several times won't get rid of this aquarium algae !.

How to eliminate Green water ?

Total aquarium blackout for 3 days or more + using algaecides. Algaecides kill algae and create a large load of waste (dead algae), therefore you should change all of the aquarium water before & after the blackout. This blackout and using algaecides can also affect your aquarium plants, fishes and crustaceans health. Some algaecides' contamination can melt leaves, stick to fish gills and kill crustaceans. It would be better if you move them first before you start the treatment. Algaefix is a well known brand which claims to be a revolutionary product that can effectively control green water and many other types of algae in freshwater planted aquariums without harming aquarium plants and fishes.

Use UV (ultra violet) filter. Aquarium UV sterilizers kill free floating microbes including algae, suitable for treating green tank which actually groups of free floating green algae. But, there are some disadvantages for extended use of the device in planted aquarium s.a UV light can breakdown some important nutrients, and the accumulation of decaying microbes within your tank.

A well maintained aquarium should be fine without one, but if you have persistent problems like algae bloom or repeated fish illness after medication, you can use the device to improve the water quality. Remember that this device can't cure illnesses!, they can only kill the microbes like bacteria, fungi, viruses and parasites that cause illnesses.

Use diatom filter. This filter can overcome the disadvantages of the UV filter, it doesn't affect plant nutrients and removes the green water without allowing it to decay in the tank. Aquarium diatom filters provide crystal clear water by using diatomaceous earth - an organic sediment with a unique pore structure that will trap the smallest debris (as small as 1 micron) !. This filter is quite expensive, can clog pretty quick and needs frequent cleaning. So, don't use it continuously, use it regularly or only when to solve particular problems.

I should say that using Diatom filter is the best method so far.

Use live Water flea (Daphnia) as algae eaters. Daphnia are small, planktonic crustaceans, between .2 and 5 mm in length. Daphnia are one of the several small aquatic crustaceans that commonly called water fleas. If you use Daphnia as algae eaters, first you have to move your fishes to other place, fishes love to eat Daphnia !. The Daphnia will consume all the green water, then you can move your fishes back after the water cleared.