Filtration, unless it's PO4 removal specific will not remove it, typically we run low on PO4 in most all planted tanks.
Algae is not related to excess or PO4.
Algae is related to things like too much light(most common), not enough CO2, (also most common), a build up of PO4 is merely a correlation of poor plant growth due to others, that, poor plant growth, is the real reason for algae, not PO4 directly.
Lack of good test methods, lack of basic understanding about algae and how to test for it has long caused these myths to keep going and going.
Focus on the plants and make sure you add enough PO4.
I have no idea what too much PO4 is, it's not toxic and does not cause algae anymore at say 2ppm than it might at 20ppm. Both are non limiting conditions, thus adding more will no longer increase the rates of growth for algae (or plants).