HELP! Huge Algae Bloom!

[samrowe]

Hello, I set-up my first reef tank roughly 6 months ago and it has gone through various algae cycles but this algae bloom is awful and hasn't cleared in about 2+ months. My tank is 600L with a 150L sump, it runs 4x T5 tubes (previously 6 but reduced lighting) for 9 hours a day. I have a Bubble Magus Curve 7 skimmer, a 40L refugium, and I run carbon and rowaphos which is changed every 4 weeks. The tank is lightly stocked with a Sailfin Tang, a blue tang, a midas blenny, a six-line wrasse and a bangaii cardinal. I do however have a small clean-up crew which consists of 2x hermit crabs, 5x snails, a cleaner shrimp, and a conch. I understand that a larger clean-up crew would help but I don't think that anything invertebrates would clear this algae. I tested my water this morning using API Liquid test kits and recorded -
0 ammonia
0 nitrite
0 nitrate
0 phosphate

I have tried to manually remove the algae during water changes but the algae on the rocks is nearly impossible to remove as its stuck down so firmly. I have included pictures of the tank in the thread.

Any advice on how to remove the algae will be greatly appreciated, thanks, Sam

[nmotz]

If it were miy tank, I might go lights out on the DT for a while and skim heavily as the algae dies off the rock. It's normal that you're not seeing nitrates/phosphates because they are bound up in all that algae. I see that you already have macroalgae going in your sump. It doesn't seem like you are overstocked either. Did you start with dry rock?

[kissman]

Are you using RO/DI water or tap water?

[pyithar]

i would not do the lights out if you have corals. are the tangs eating those algae? cuc don't usually eat long algae. if it's possible, you should take the rocks out and try scrubbing them again. in the mean time, try to reduce the nutrients. look into vinegar dosing and algae scrubbers. i believe they'll be big help.

[kissman]

Lights out with corals is fine happens in the ocean all the time