DSB in both my reef and my fish only. They do not need to be cleaned especially if they have the diversity to do the job themselves. The only time I've ever used a syphon since establishing my dsb's was to manually remove some cyano that appeared briefly in my reef. Stirred it up and syphoned it out. The critters in the sand do a very good job of keeping things clean.
But if you are using crushed coral...then it may be necessary to syphon with each water change...maybe even more frequent....crushed coral tends to accumulate detrius and gunk that a established DSB will consume.