green water algae

Question
i have a 55 gal w/ semi auto co2, 3 vho 48 inch lighting tubes,penguin 350 filter using cotton type filter and renew carbon substitute in filter and small powerhead w/ quick filter. using r/o water and add 1/4 tsp per 5 gal of r/o right all water perameters are ok. have been doing 40% water changes /week and adding algaefix as perscribed. i have 4 small swords, anubis(3) and 2 java fern,3 bunches ludwiga, and 4 bunches monetwort and 1 bunch of new Polygonum sp. Sao Paulo. the green water just keeps comming back hours after water changes. doing gravel vac and cleaning the whole filter. i am at my witts end and i need your help. should i leave lights on?turn off co2, no bubbles at night, new bulbs  (5 months old) just dont know. please help. i have a black ghost knife 10 inches long and they are sensitive to chem. and is my pride and joy, so ihave to be careful. thanks in advance

Answer
Hey there,
seems like your a pretty knowledagable guy...

well first off.. dont worry pretty common thing believe it or not, you definately have some param errors... but i cant tell you exactly what it is.. definately a bloom of some sort.

You have 2 options here... go out buy a uv sterilizer.. and it's solved.. problem is.. you dont know what's causing it.. even thought your killing all the algae does not mean the root problem is not there still.

second option:
do a 48 hour blackout, totaly black your tank out for 48 hours without peeking.. keep it totally black. after that point then unwrap it.. and see if the blooms still there.. if it is... wait another 48 hours.. by blacking it out.

I would minimize your lighting immediately though.. cute it out by 2 hours a day, minmize feeding or overfeeding...

Test all your params  and figure out what is causing this.

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