Unofficially, I placed the 12" riptide vertically in my 48 gal office tank. The tank is only 17.7" tall with a .5" sandbed. I placed it on the right side back pushing water from right to left across the back and then creating the gyre towards the front and then heading back to the right side of the tank for the full cycle. At speed 7, I had no issues with the sand bed.
At higher speed I had issues with the sandbed on the left side back and left side front but was mainly because the tank is only 35.4" long. The pump was way too much at speed 7 or higher for my small size tank. We have tested it in 4' long tanks and there have been no issues with the sand. Tested in a 8' long tank and no issues there. Both the 4' and the 8' were tested at full speed.
Hope this helps, unofficially of course... ;-)