I have always read and experienced water changes to have little effect on lowering phosphatesWhen you change your water, you are lowering your phosphates...when you add your liquid remover, you are further lowering them. This is fast change in water chemistry can have an adverse effect on your livestock. I'm not even sure why you are using it? As algae grows in your tank, it will use up the phosphates...which is a good thing.
But will significantly lower nitrates .
A phosphate removing media such as rowaphos or even using cheato has always worked for me

