No filters will reduce the mineral content. Sometimes a portable water softener can help, but it only substitutes minerals which don't participate out for ones which do. I don't think they help with tank corrosion, but am unsure on that.
You mentioned an anode. The Atwood heaters do not recommend them, although they are available from other sources like Camco to fit the drain plug. There is a possibility that they do more harm than good, from what little water chemistry I understand. This is due to the fact that the tank is aluminum. So, there is a possibility that your use of an anode is not what you should be doing.
Suburban tanks are glass lined steel, and they do recommend an anode, and frequent replacement of it. I doubt that you have a Suburban water heater though.