if you have sand you really shouldnt have to clean it. the critters in the sand should do it for you. even with the lr critters will move from the rock to the sand and vice versa. they eat all the junk on the bottom and off the rock
It might be a good idea to get a detrivore kit as well so that you have an abundant population of critters to help clean the sand bed. Check out www.ipsf.com and www.inlandaquatics.com
You should do searches on this board for "DSB" and "deep sand bed" to make sure your bed is configured properly. Lots of new hobbyists start out with a grain size that is too large, and won't function properly as a live sand bed. Even if the bed is not "deep" it should still be constructed with sand of the right particle size so that it is self-cleaning.
I would imagine that in many people's FOWLR tanks the detrivores have no chance of survival in any numbers. Wrasses, etc will pick the rock clean in no time. That said, I have never attemped a FOWLR tank and can't provide any sagely input, but if you see a real buildup on the gravel of waste, I would consider vacuuming it out to prevent high ammonia/nitrates.
actually if you do get a det kit put it in first before adding fish and let it go for about 2 weeks. during that time put food in the tank and it will dissapear quicker and quicker when the food is gone in about a day that means they are taking a good hold. you can add them even with fish feed the fish well, turn off the light so the critter can get to the sand and rock also turn off your filters or pwr heads for a little bit