green water help!!!


Junior Poster
Mar 19, 2008
i have a 65 gal 36x18x24 tank set up for about a month and a half and planted for 3 weeks. for lighting it has 3x39watt t5ho but i have reduced it to 2x39watt for 8 hrs per day due to green water. i attempted a 3 day blackout and the tank cleared but 1 day after the lights were back it was pea soup again. ive been getting mixed advice on what to do so any help is appreciated. the tank is moderately planted and i have added some fast growing plants but it doesnt seem to be helping. i was dosing ei for a 40-60 gal tank plus adding 3/4 tsp of gh booster at water changes. currently i have stopped dosing ei for the last week to try and get rid of green water with no effects. What is the cause of green water and how do i fix it.

Tom Barr

Staff member
Jan 23, 2005
Borrow, rent or buy a UV and that will be the ned of it inside 2-3 days and it'll never come back again for the most the part.

Mainly a new tank issue.

Diatom filtration, micron filtration etc also works well.
Folks with high light, pc lighting etc gert it when they do not add enough plants, or mess up the CO2 etc.

No matter what anyone says, you are not going to limit this algae, so you can forget not adding nutrients, it will not make this algae go away.
Folks have tried for months without dosing, no effect.
Blackouts also.

Not enough plants, too much light and poor bacterial colony = GW everytime almost.

It's one of my model algae I like to work with(easy to get rid of, does not real harm to plants, and easy to induce and homogenous(even throughout the volume of the infested tank).

See if you can borrow a UV etc.

Tom Barr