I don't think you will have to do that once a month. Maybe once every 6 months or once a year that might be beneficial, but there are problems associated with doing that.
You can use a turkey baster to blow off the rocks while they are in your tank....You can even hook up a filter with carbon or something once a month and blow it off and let the filter remove most of that stuff but this isn't needed.
Most of that stuff is just fine to be in your tank, though. Think about where all of that goes in the ocean. There is no mechanical or chemical filter in the ocean, everything is broken down by the biological filter, and that is usually the end goal in our systems as well. Because of our limited water volume and certain other things, we DO have to run some mechanical or chemical filtration sometimes (i.e protein skimmer) but you don't need to compulsively clean the rocks off.
I usually blow mine off with my Coralife 21" feeder about once a week. It gets the tank kind of cloudy for a few minutes and then it settles back down. The point of this isn't to remove it from my system, it's to stir it up and move it around so that all my little detrius and scrap eating critters can more readily get to it...and they do a good job!
As time progresses I will likely need to do some sort of mechanical filtration when I do it every once in awhile. A simple biowheel filter or my old canister filter will do the trick for a couple of hours at a time, but until then I probably won't do anything about it.
Another thing to remember is that if your rocks are glued or if you have coral, removing the rocks can really be a pain in the ass. :-)