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[surgio]

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[debbeach13]

If you are looking for a chemical solution, I cannot offer any advice. I would rather manually clean the rocks several times than add chemicals. I just don't trust them to be anything but a temporary solution. Others can suggest what has worked for them. What is you water source? Tap, bottled distilled, RO/DI?

Do you still have the crab, fish, and snails?

Snails, snails, snails, maintain a good mix, different snails eat different things. To me it looks like you are going to have to manually pull out as much as you can, again. I have not found any livestock that eats long algae, but my emerald crab and turbo snail keep algae under control once I get most of the long stuff under control. Turbo's can knock any loose frags about. Make sure any frags on the rocks are glued down. The turbo spends time on the rocks and glass, He does not clean the sand at all. Zero nitrates and phosphates are a concern. It is most likely being used up by the algae. I am happy to see your corals look healthy. Everything is open with polyp extension.  Algae and corals use the same nutrients so at least right now the algae is not out competing the corals.   Next time you mix up some new saltwater test it before you use it. 

I don't know if any of that helps you. I run a kiss set up. I only use activated carbon and filter floss, with weekly 10% W/C. 

Hang in there you can beat this.

[debbeach13]

Randy Holmes Farley’s 

Optimal Parameters for coral

hope you can read my chicken scratch 

[Pjanssen]

looks like bryopsis to me. Very difficult to get rid of. You can try a 3 day total blackout. I used fluconozol (reef flux) with success, there are many threads about it.

[mcarroll]

It looks like you aren't removing any by hand.  Even if you have a cleanup crew, they can't deal with algae that has been allowed to grow long.

 

It also looks like your rock is REALLY CLEAN.  That means every square inch is ready to be populated – and green algae are (often) the most capable of doing it.

 

We're going to have to work on reversing those two things.  Once complete, your algae will be under control.

 

REMOVAL BY HAND

If you aren't doing this already, now is the time to start!  🙂   

 

If you already are doing this, then it's time to double down on your effort and maybe get a little more systematic! 😉  (see video link below) 

 

TANK TOO CLEAN

Is your water too clean?   NO3 ≥ 5.0 ppm and PO4 ≥ 0.05 ppm would be good minimums.  With levels lower that this you are going to have trouble growing anything to cover your rocks other than green algae.  The green algae will remain comfortable even if you take all nutrient levels to 0.00 ppm on your test kits.  Don't bother.  If your levels are currently lower than those targets, eliminate enough filtration and cleaning activities to allow levels to come up.  If that's not enough to restore proper levels, you can consider dosing nitrate and phosphate for a little while.  It's very effective, inexpensive and safe.

 

Your rock is definitely too clean.  Might have been too clean even before you scrubbed it.  😬  Not a lot you can do about this now, after the fact.  Ideally, don't start with dead rock – then available space for algae to settle should already be minimal.  If you have to use dead, give it lots of time to grow in before you add any major bio-load or a lot of light.  (google periphyton)

 

Thankfully, I suspect you have a third option available...

 

HERBIVORE SNAILS

You didn't mention cleanup crew once in spite of rebooting the tank once already.  I suspect you don't have one or don't have enough....or maybe have the wrong critters.  You are going to need Turbos, Astreas, Trochus and/or Cerith snails or the like.   Avoid scavengers...

 

One more thing....

 

LIGHTS

If possible, turn your lights down.  NOT A BLACKOUT tho.  Turning them down to the right range for corals (ie low) will slow the algae down a little if the lights are brighter than needed.   10,000-20,000 lux / 150-350 PAR is generally plenty....more is usually NOT better....even where corals are concerned.  You can opt for the lower end of those ranges...or even a little lower if you want.  👍

 

...and now that video I mentioned.   Pay attention to the method he uses for getting the algae out of the tank AND the guidance on snails.   (Disregard the other advice which won't apply.)