I posted this in another thread, but I have the same problem in a 75 bow front.
I got a large turbo from Petco, and several smaller ones. About 25 bucks worth.
This payed off in about 3 weeks.... the "KONG" was blazing trails about 2 inches wide and the smaller guys worked the sided and the rock. "KONG" would clean a rock in ohhh about 10 seconds..
Anyway... once cleaned... I returned the big guy and kept the small ones. They took him back....
Keep in mind... I was starving my fish with very small food quantities.
Here is "KONG" and a smaller turbo... for size reality!!
Its sweet and safe
Mike in Myrtle Beach