Since your pH is quite high, I suggest mixing tap water and spring water in various ratios and see if the pH level lowers. According to several sources I have in my frog library, ACFs prefer a pH between 6.0 and 9.0, with optimum levels slightly alkaline between 7.4-7.5. I understand that it is much easier to raise pH then to lower it, maybe Jenna has some ideas.

Sources:
The Laboratory Xenopus by Sherril Green
Guidance on the housing and care of the African clawed frog by Barney Reed (available online in PDF)
The Biology of Xenopus by Tinsley and Kobel