Hey everyone,
I’m looking for some advice on this rust-colored algae growing on my sand bed. It looks like a slimy layer and tends to sit mostly on the sand rather than the rocks.
I do know a CC would help but the tank has a mantis shrimp and I know they wouldn’t last long so I’m trying my best to not get a CC.
Parameters 3 days ago:
• Nitrates: 0 ppm
• Phosphates: 0.2 ppm
I started dosing nitrate at about 1 ppm per day.
Parameters now:
• Nitrates: ~3 ppm
• Phosphates: ~0.1 ppm
• Calcium: 460 ppm
It seems like phosphate dropped slightly after nitrate became detectable.
Does this look like cyanobacteria, or could it be something else?
Any tips on the best way to handle it?
Tank is a 40 breeder, recently reworked the rockscape as well if that matters.
Here’s a photo

I’m looking for some advice on this rust-colored algae growing on my sand bed. It looks like a slimy layer and tends to sit mostly on the sand rather than the rocks.
I do know a CC would help but the tank has a mantis shrimp and I know they wouldn’t last long so I’m trying my best to not get a CC.
Parameters 3 days ago:
• Nitrates: 0 ppm
• Phosphates: 0.2 ppm
I started dosing nitrate at about 1 ppm per day.
Parameters now:
• Nitrates: ~3 ppm
• Phosphates: ~0.1 ppm
• Calcium: 460 ppm
It seems like phosphate dropped slightly after nitrate became detectable.
Does this look like cyanobacteria, or could it be something else?
Any tips on the best way to handle it?
Tank is a 40 breeder, recently reworked the rockscape as well if that matters.
Here’s a photo
