You must have a really high concentration of iron in your water. I have iron in my well water too. I have an inline house filter from Home Depot, and use a carbon filter cartridge in it. Depending on the brand of cartridge, we can get a few weeks use out of a cartridge before replacing. I usually change the cartridge when the water starts to taste bad.
Not sure what else you could use other than RO.
I have bad iron as well. I use a carbon filter on my fill hose. The water still tends to be cloudy for a few days after. Very frustrating because it will start to be nice and clear and then it's time for a water change