Can you run 2 UV Sterilizers on the same tank. one for algae and the other for parasites, both being fed by separate pumps. Would this work or is it a waste of effort?
Same water is going to go through both. I don't see a value in 2 separate UV's unless you are going for "extra size" and a larger wattage unit is not available.
You can and I see the point. But at reasonable tank sizes, it's probably cheaper (more efficient) to run a slightly larger UV with an variable speed pump that covers both.
Full disclosure - running a UV in my return line with variable dc pump. It's not perfect (sump flow is higher than I like for dino control). Next tank will have closed loop for UV with variable pump.