GHA on one rock ONLY

[AcroFan144]

Hello,

I am have a problem in my 4 month old setup. I started it with all dry rock and 1 piece of ocean live rock, covered in sponges and coralline.

GHA keeps growing long strands on that live rock piece only. Other rocks , which were dry and cured for 2 months before placing in tank, are completely free of algae.

NO3 is 0 (Salifert), and PO4 as well (Hanna ULR phosphorus).

I use a filter pad, skimmer and macroalgae for filtration.

Is it possible that the live rock piece is leaching PO4, allowing GHA to grow on it? As I said, all other rocks are completely algae free. If so, how long will it take for PO4 to leach out?

There are no corals in the tank curently, as I am planing to finish my fish stocking before geting corals,

Any tips on how to deal with the situation? I tried to scrub the algae once, but it came back in a week.

Thank you for your help!

 

[Ron Reefman]

Try scrubbing the rock again and then give it a 10 minute dip in hydrogen peroxide (assuming no corals or other life you want to keep. I've done 5 minutes dips with zoas and RFAs and they were fine. After you dip, it would be good to keep the rock in isolation for a week or so as the last of the algae dissolves and comes off. I've just finished doing this with 2/3rds of the rocks and corals in my tank. I took 4 rounds as I could only do 25% of them at one time.