I use Reptisafe as well and have never experienced bubbles from its use. However,I have experienced bubbles/foam when adding new water features and using rocks that weren't rinsed properly. Foam comes from organic material in the water.
This may be weird, but I use Reptisafe to wash my hands before handling my frogs. I put a few drops on my hands and rub them together like a soap, then I rinse and spray my hands with treated water... I find it dries my hands out and removes any oils I have on my skin. It seems to work well.