I bought my first gun safe a few weeks ago and it's in a garage that is not climate controlled. I placed a 12" golden rod (GR claims up 100cu/ft of protection) in the safe. For the time being I also left the desiccant bags in that shipped with the safe. I also bought two temp/humidity gauges to help me as well, one inside and one outside safe. So I have some sort of way to gauge the climate in the safe relative to the garage.

I think I may be doing it wrong with the desiccant and the GR being combined in the same space. Thoughts?

Suggestions, thoughts, theories welcome!

The GR works by heating the inside of the safe, essentially forcing colder air/moisture out of the safe. The desiccant works by absorbing the moisture. There is absolutely no issues with using both, you'll find the desiccant just lasts longer before needing to be recharged.

You’re already doing the right thing by actually measuring the humidity inside your safe and doing something to control it.  This will tell you if your goldenrod is enough, if not, upsize it to a larger unit.

Overall ideal relative humidity for a gunsafe is 50% from what I have read.