Pull the impeller out & give it a good clean. Pull all media out of the filter, & keep it wet with tank water. Clean out the intake tube & case with a good blast of tap water. This should get any sand out.
Get a sponge intake prefilter to cover the intake. This will keep sand out. If you have a spare ac 200 sponge, poke a hole in it & slide it over the intake. I have ac 200's on my 29's, and use the sponge to keep young angel fry from being sucked up.