The products out there are designed to take your money and break the foam down.
Many here will suggest if you want to get rid of the foam, STOP introducing it. What you "wear" into the tub has residual soap still in the fabric. IF you are unable to wear your birthday suit, then wear the same thing all the time without washing it with soap. Once the soap is rinsed out after using the hot tub they should be OK.
IF you have alot of foam, turn the air blower on and get the shop vac out and connect the blower to blow it off the surface and out of the tub, or get more "defoamer".