When thinking of algae think light, NH4 and CO2. These are three triggers that will cause algae to bloom.
Phosphates will not cause algae in your tank, but they are used as a nutrient. I add phophates to mine to keep levels up for the plants, and I get no algae. I can increase the dose above target and stiil there is no algae.
Add daylight to a glass of water and you will get algae. Add daylight to a glass of RO water and you will get algae. If I turn the CO2 off in my tank, or reduce its levels below the plants requirements, or cause it to fluctuate I get algae (staghorn and BBA). If I carry out maintenance that disturbs the substrate, or prune down the plant mass considerably, small levels of NH4 result, and I get spirogyra algae.
If you remove phosphates from your tank you are removing a plant nutrient. Ultimately, this will affect your plants adversely, resulting in your plants leaching NH4 and making the algae outbreak worse.
All alga are different, but starving them of nutrients will see your plants off way before the algae (I can grow algae in water with a purity of 0.02mS/cm).
Is the algae easily removed by rubbing the leaves, and is it only on the Anubias? Do the plants with the algae appear healthy?
Dave.