I'm gonna chime in as I fought a battle with algae for over a year. Finally I'm winning.
First, algae LOVES water movement. Bacteria like Cyanobacteria hate water movement but hair algae loves it. More movement means fresh nutrients brought in.
Like you I also had 0 nitrates and phosphates, fed very little (which led
to a few crab and shrimp deaths) and reduced lighting. Completely removing lighting will not get rid of algae (therefor neither will reduced lighting) but it WILL help slow the growth of new algae.
[I put half my rocks into a 25 gal
curing bucket with a lid, heater and water movement, did periodic water changes to keep nutrient levels very low, and after 4-6 months with absolutely NO light the rocks were still covered in algae]
The ONLY thing I found that got rid of algae that was already there was manual removal. Now there was no way I was going to tear apart 150 lbs of rocks, so I hired some help. A ton of hermit crabs, who attacked the algae with vigor. About $200 of hermits for a 110 gal
tank from a wholesaler (about 1/2 price from a LFS
). Scarlet and dwarf blue leg crabs mainly plus a couple electric orange. I avoid dwarf red leg as I find they eat all my snails.
Also check your Alk
and Calc levels, as low numbers there can lend to algae growth.
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