No, but it’s a good idea for a few reasons.
First, once you move it you’ll reveal a clean, clear, natural lake bottom with no weeds. It’s much nicer (and more interesting) to look at a real lake bottom rather than a Mat.
Second, you’ll get rid of a lot more weeds over the summer. If you leave a Large LakeMat in one place, it covers close to 32 square meters. If you move it once a month you’ll have about 120 square meters of weed-free area by August.
Third, moving it through the water washes much of the sediment off that’s landed on it. If enough sediment builds up over time, it creates a base for weeds to start growing on top.