I often really wish you would stop pugging Aquaclears. What they were back when they first hit the market is not what they are today. Cheaper parts, flimsier bodies...etcWELCOME TO TFK!!!
I have a couple of Aquaclear 70 HOBs on my 60g and have a [pool filter] sand substrate and have never had a sand problem in the filters.
Is your sand too fine so it's easily raised off the bottom or as mentioned, is your intake tube too low/close to the surface of the sand?
Perhaps your sand wasn't rinsed/washed well enough to remove the finer sand particles?
All my tanks had sand, and even with the intake well pulled away and with well rinsed sand these things would kick the bucket quite easily. I see used ones hitting one of the local stores every day.
To OP, you need to ensure that your intake is well away from the bottom. Putting a pre-intake sponge onto the intake can help but it will be rinsed from time to time. My best suggestion is to get a Canister and get one that pulls water through the canister and through the media first, and then it goes through the impeller/into the tank. This prevents sand from hitting the impeller if any does get in and problem solved.
Don't get Aquaclears unless you want to waste money and time.