Just curious what is the longest amount of time that is safe to go lights out to get rid of algae? Currently just have zoas, GSP, xenia, false perc and a condy nem...and alot of GHA and cyano.

i would say lights out is not a solution to your problem. Lower nutes, increase flow and manually remove.

I feed very little every 3 days, and have no dead spots as far as flow goes. I got the algae unfortunately as a hitch hiker with LR from an individual out of their established tank. I have tried raising MAG to get rid of the bryopsis with reasonable success, but at the rate the GHA has grown, i will soon have no uncovered portion of LR even with daily manual removal. (during the first 2 weeks of setup I admit I probably overfed but has been GREATLY reduced to help rid the tank of the pest algae) Right now I am just looking to remove light for a period of time to speed up the process of getting it out.

I would say you need to lower the algae nutrients (nitrates), even if there undetectable w/ a test kit b/c the algae could be using up the nitrates b4 it gets to your test kit. As you probability know cheato is a great nitrate exporter, run some if your not already. Water changes are also a great way to exprot nitrates. The GHA still wont get rid of itself after you take its nutes away so manual removal and the help of some CUC will be needed, turbos are great for this... just make sure there are no frags to knock and the rock work is stable. I think lights out wont help you out in the long run.

To answer your question.... 3 full days is the accepted practice.

+1

How much are you feeding the condylactis and everything else? It's not good to keep an anemone in a 1 month old tank.