04-06-2013, 02:27 PM
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Some reliable dataz on "green water." First is by George Booth, second by Dusko Bojic.
Green unicellular algae will sometimes reproduce so rapidly that the water will turn green. This is commonly called an "algae bloom" and is usually caused by too much light like direct sunlight. An algae bloom can be removed by filtering with micron cartridges or diatom filters. UV sterilizers can prevent the bloom in the first place. Green water is very useful in the raising of daphnia and brine shrimp. Film algae Grows on the aquarium glass and forms a thin haze. Easily removed by wiping the glass. Considered normal with the higher light levels needed for good plant growth.
The situation that causes GW (Green Water) is usually a combination of high nitrates, phosphates, and mixed in some ammonia/ammonium. Substrate disturbance is usually the culprit. What happens is the algae (GW form) will flourish off of the ammonia/ammonium and phosphate, remembering that algae can consume phosphate easier than plants because of their thin cell walls, the algae uses up the ammonia/ammonium and phosphate, but it doesn't go away...because algae can quickly switch with nutrient it scavenges...it moves to nitrates. So you can see why water changes will not rid a tank of GW. Nutrients can be reduced very low in GW and fairly quickly by the GW algaes, but they can scavenge other nutrients...iron and trace elements. So, it's very common for the GW to solve the situation that causes it to begin with, but that won't eliminate the GW, for the reasons I've allude to. Five methods exist to eliminate GW. Blackout, Diatom Filtering, UV Sterilization, Live Daphnia, and Chemical algaecides/flocculents. The first four cause no harm to fish, the fifth one does.
Since "green water algae" thrive in water with NH4 and strong lights, I planned to add floating plants to shade the tank (something like black-out) and to uptake the NH4 from the water column.
As both authors indicate, high light is a prime concern with this as indeed with any type of green or red algae.
Adding more nutrients is not going to help. But having said that, the plants must receive sufficient in order to be able to out-compete these algae. Your light is still an issue.
Adding chemicals of any sotrt, be it flocculants, algicides or Excel, is not wise; all of these do have an impact on fish.