Is it common to run any chemical media in a tank? I have a reef tank with Renew, Purigen and Phosguard. Currently only running the coarse mechanical filter, some filter floss and the bio ceramics that came with my Fluval C4. Would adding something like Renew (artificial carbon substitute) be beneficial at all?
Purigen removes many types of organics, polishing the water in the process. So, it helps reduce organics that will turn into ammonia, nitrites and nitrates. Seachem does not know if it will remove organic phosphate (before it becomes orthophosphate), but it will not remove orthophosphate.
Phosguard removes orthophosphate, only, not organic phosphate. However, in a planted tank, we want a certain level of PO4, so don't try to eliminate it. Use it for the plants. Try to keep it in the area of 2-5 ppm and get to know the EI (Estimative Index) method of fertilizer dosing. In fact, check this out: Planted Tank Guide
You're in a new world now, moving out of the reef world, and will need to pay attention to light and CO2 issues as well as ferts.
Renew is a better than carbon and will remove heavy metals just the same way carbon does, although it will not have as high of a capacity. It is also different from carbon in that it won't release phosphates once filled. It will remove chelated products which we often need in our ferts. You shouldn't need Renew or carbon unless you are removing medications.
Stick with Purigen, which will help with the organics burden and almost guarantee crystal clear water. Technically, you don't need it, but it helps. I use it at half recommended dose and I also have no bio-media in my filter. My plants and substrate do all the nitrogen cycle work, but you have to build up to that. The only thing in my filter, other than the half-dose of Purigen, is the mechanical filter.