Metals have anti-algaele (sp?) properties, but the risk is that they can cause staining. Chlorine alone is sufficient, and if used properly, the active chlorine level is very, very low.
Most pool builders really like high HP pumps, when the greatest efficiency is achieved with a very big filter and a minimized pump. The flow rate is lower, which improves filtration, and the electrical draw is reduced. I saw significant savings on my electric bill when I went from 1hp to 3/4hp. My pump run time was nearly unchanged, my pool was just as clean, and I couldn't tell a difference in the flow rate by feeling the water at the return. So basically, nothing noticeable changed in my setup except the cost to run it.