This is basically what I do. I, very lightly, siphon the sand but remove a bit each time. Once it gets low, I'll slowly add new sand. The biggest problem with small grain sand is it getting blown around in high flow tanks. From looking at the picture though, it looks like you're using a pretty coarse sand. I'm using Fiji Pink which I like, but I do have to be careful with flow and I do end up with bare spots after several days that I have to push sand back in to. I've used super fine sand in the past and it's awful (detritus trap with no way to clean). On the opposite spectrum, I've used crushed coral and it's also awful (it get really ugly IMO).
Sand is one of those things you'll get a thousand different opinions on.