Plants need phosphates. It's been shown that phosphates are not the root cause of algae as they were once believed to be. I have 1-2 ppm of it in an of my tanks at any given time, but others have more.
If a person has a ridiculously high amount of phosphates, in their tap water for example, a phosphate reducing product might help get the phosphate level to a non-ridiculous amount, but you don't want nil phosphates either. Although phosphates are needed for plant growth, at some point having more does not induce better plant growth, nor does it particularly lead to any problems in marginal excess. Phosphate removing chemicals don't differentiate between a healthy amount of phosphates and a possible less- than- desirable amount, however, as it will seek to remove ALL phosphates.
Have you ever tested phosphates to determine a need for a phosphate reducing chemical? Things may be working alright now, but you might find it difficult to maintain your current success if you're limiting phosphates too much. If a person is seeking to limit anything to reduce algae, usually reducing lighting is more desirable. This will reduce the nutrient demand of the plants and give more stability to the tank, especially if the plants are not intensity hogs in the first place.
A person does not have to have any sort of chemical filtration if there is no particular need for it. Carbon is good for some things, but myself and many others have found it to be purely situational and optional.
What sort of algae were you having problems with before? Phos-zorb removes silicates as well, so maybe you had some algae spurred on by an excess of silicates?
Phos-zorb is primarily for fish-only type freshwater tanks or marine tanks where phosphates do not particularly serve a purpose if not being used in a buffering capacity.
"Good judgment is the result of experience, experience is the result of bad judgment." --Mark Twain