Yes, purigen reduces organics so it will help.
However, I have an 11" common pleco and have no problem with nitrates, in fact I add KNO3 to the tank. However, I've been doing 50% water changes weekly for years. For a CO2 injected tank such as yours, it's almost a requirement because the waste in the tank produced is higher. Plants too can produce waste, especially if not healthy.
I am not sure how large your tank is, but I'd double check how you measure nitrates because those home tests are very inaccurate and can be way off the real truth. In a heavily planted tank nitrates are a big plus.
The problem with fish is high organics, not the final product of organics which is nitrates.
So if you want to reduce organics, clean up the substrate, the filters regularly, regular water changes, Purigen helps reduce organics too.
Make sure your pleco receives a proper diet, if a herbivore for example, make sure it's not gorging itself on blood worms and such.