Cant get Phosphates down

[sphelps]

What kind of red algae? It's not cyano is it?

[WindowMaker]

red sheet on the bottom. I think that is cyano...

[Douglas]

Do you have sand? and option is to remove it. Go bare bottom. I've never had an issue, with Phosphates, with a bare bottom tank. But that's just my opinion.

[sphelps]

Originally Posted by WindowMaker

red sheet on the bottom. I think that is cyano...

yeap that's cyano, it's actually more like bacteria than algae so cutting phosphates back will have little effect. The best way to deal with it is by removing as much by hand as possible and then using a red slime treatment such as chemiclean.

[George]

How big is the tank? How many fish and what type? How much do you feed them? Is it possible to cut back the feeding?
GFO works. You might not use enough of it. Increase your GFO. measure the effluent from GFO, if PO4 is not 0, change your GFO.
Grow macro algae in ref or building a algea scrubber.
keep up with water change.
Your rocks may leak phosphate if they were in high PO4 water previously.
liquid or solid carbon dosing will help, but they need nitrate. You don't have any nitrate. Is your nitrate value correct?
Skim wet.
Some use Lanthanum Chloride with success. Google it because you have to be careful using that stuff.
Good luck.