Brown Slime on my Sand and Rock! Help!

Hello Everyone-

If I don't have bad luck, I seem to have no lick at all! First I had an issue with slight current in my tank (thanks for the advice Tangster!) and now I have an algae issue.

My wife called me at work to say there was a problem with my refugium in my tank when she got home from grocery shopping. When I got home, I found about 5 gallons of water on the floor. What happened was a chunk of Chaeto dislodged from the main part of the refugium and took a trip over the falls to get lodged into the output of the refugium. So, water kept going into the refugium but didn't come out! My wife basically unplugged everything in a panic. When I finally found the problem and rectified it, I noticed there were patches of brown slime algae on some of the rocks and my sand.
My water parameters are fine: pH 8.3, Ammonia/Nitrite/Nitrate are all zero, phosphate < 0.1, and temperature is 75 degrees.

Should I shut off my lights for a few days? Will my corals be ok? How many days do you think would be safe?

Thanks in advance everyone!

 

2 questions since the flow issue is likely resolved after Tangster's advice

1: How old is the tank
2: Is any sunlight hitting the tank?

What you likely have is Cyano not actually an algae outbreak which needs to be treated a little differently

 

Thanks for the help guys!

I think my flow issue is ok; I still keep coming back to my lighting. I have 6 t5s in a Nova Extreme Pro fixture, 3 are actinics, 3 are daylights. This tank does receive some natural sunlight, but the cyano really starts to show up once the daylights turn on. I reduced the photoperiod to 8 hours with the actinics turning on/off 1 hour before/after.

Thanks for directing me to the cyano articles!