What about silicone the pipe directly to the tank glass...you'll have to transfer the turtles for a couple days while it all sets, but shouldn't be an issue after
Get a couple of these suction cups from Harbor Freight and zip tie the pvc onto them. Paint everything with Krylon Fusion spray paint if you want it more inconspicuous. View attachment 1224323
I've made DIY intake holders for my Eheim 2260/62 filters using either acrylic wreath holders or cutting and bending 1/4" acrylic to size. Here is an example from another forum: http://www.cichlid-forum.com/phpBB/viewtopic.php?t=243443
Some possibilities for the intake strainer guards would be metal hardware cloth spray painted with a fish safe coating (since this is a turtle tank) or a larger diameter PVC pipe (3" to 4") that could surround the strainer itself and still allow good water flow into the intake, just drill some additional holes in the pipe.