How do I get rid of this red algae?

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Aquarium Advice Apprentice
Jan 15, 2013
How do I get rid of this algae? I have 2 10 K T5 HO metal halides as well as actinic. the whites are on from 6 Am to about 6 PM, and the blue are on at 6, and off at 6 pm. 20 gallon tall and lights are about 4 inches above the top of the glass evap. I have a skimmer, don't over feed and everything looks good, but this algae is in there and taking over and covering my corals. It's in my 14 gallon biocube too and it's lights are white with no blue and this same red algae is in there too. I thought maybe it was the blue but it's not. Help?


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12hr light is bit much so cut down and see if that help. How old are your bulbs. Are your test good. What wc are you doing as if in both tanks something you could be doing ain't helping. If you go down the page there's other thread that might help you out
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That is cyanobacteria. Aka, red slime. It is a nutrient issue. I would suggest cutting back on feeding, I feed twice a week, along with water changes with ro/di or ro water if that is the best you can do. Increase flow and cut back light to 8 hours...but it is mostly a nutrient issue.
3 days of no light will get rid of it but will come back if you dont find the source of the problem. Feed only 2 or 3 times a week. Make sure you rinse you food before serving. Do 20 percent water change. When you do a water change siphon as much red slime as you out. This should work. Maybe consider getting a gfo reactor, Skimmer and rodi if you dont have any.
I found that 3 days of no light didn't help when I had it but I cut back on feeding, removed as much as can and done 30-40% wc twice a week helped
well, I have a skimmer, and use distilled water. I don't feed anything in my tank except my clown and a few shrimp pellets for my goby. I will cut back on the lights, they are about 8 5 weeks old. I changed all 4 at the same time. I first noticed it in my cube and cut the blue light completely and it's better but not gone. I did transfer some water from it to my reef a few weeks back so maybe there is a connection.

how many hours per day of white/actinic do you suggest? I have several corals:

Open brain
glove palm
orange sponge
red and blue mushrooms
leather finger
hammer head
maxi mini carpet
a tiny red bubble tip nem
a tiny red nem that I forget the name of,lol but it's really sticky to the touch
2 sea fans
one toadstool leather
palm tree looking corals (I forget the correct name)
3 feather dusters
cleaner shrimp
2 hermits
1 dragonnette with a hearty supply of amphopods
and a phantom clown

I top off water as needed, so would water changes be better? I know something is out of whack but I don't want to throw everything out of whack,lol. Thanks for all of the replies so far.
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