I have heard that Africans do like higher PH but 8 seems a little excessive. I would make sure that whatever the median PH requirement is that you target the middle of the PH requirement for that species. The key is the PH requirement not whether your water is perceived as hard or soft which is a loose term anyway, PH-PH-PH. Now to get to the middle of the target if it requires coming down I recommend the use of some
RO water with water that high to bring it down. The percentage you will have to experiment with and then followup with the proper mix at each
water change.
Remember that Africans are considered sensitive to even tiny amounts of
ammonia which is actually a myth. The reason Africans die so easily even undetectable amounts of ammonia is because of the high PH which almost immediately allows the release of deadly
NH3 as soon as ammonia is present. So be on guard with Prime and consider using small doses at every water chnage as insurance.