The East African island nation has a reputation of being one of the more relaxed Muslim countries in the world. Its famous beaches and tourist hotels play host to visitors from around the world.
That may be ending soon, as this Financial Times report would seem to indicate:
Al-Noor charity, set up four years ago with money from private donors in Dubai and Saudi Arabia, is among a clutch of new foreign-funded religious institutions to increase its investment on the island. As well as the radio, it has established a mosque, internet rooms and a nationwide network of madrassas. It plans to build more, and every year pays for students and teachers alike to study in Sudan, Abu Dhabi and Saudi Arabia.
Academics estimate that Saudi Arabia - where Wahhabi Islam is practised - alone spends $1m a year on Islamic institutions in Zanzibar.
"Wahhabi madrasas are just starting - they are now many and Saudi funds are spreading their work - they have nice buildings, they are well off and well organised; they preach and convince the parents to come there, so the effect of the madrassa is very powerful," says Idrissa Ahmad Khamis, a teacher who is from the Sufi tradition, a mystical form of Islam opposed by more literalist Wahhabis or Salafists.
Al-Qaeda and other terrorist organisations draw their thinking from Wahhabism. "We're not happy with other sects like [Sunni hardline] Wahhabi - people who go to countries like Saudi Arabia; when they come back they want to change everything," he says.
Past attempts to introduce Wahhabism have not been successful, says Jussa Ismail, a parliamentarian. "But it's very difficult for the traditional madrassas that are in really poor shape to rival the influence of those who are being funded by foreigners and Wahhabi-based institutions," he says.
Few Zanzibaris admit to hardline views but now "some parents are sending their children to the new Wahhabi madrassas on the pretext of needing extra lessons", says Shakra Hassan, an unpaid instructor at an underfunded madrassa.
Washington has helped build pre-school madrassas throughout Zanzibar and last year spent part of its $76m counterterrorism budget for Muslim communities in Africa on textbooks and teacher training in Zanzibar.
Saudi funding for conservative religious institutions comes amid a government crackdown on Uamsho, a group advocating greater observance of Islam and for independence for the semi-autonomous islands, part of Tanzania.
Mr Ali denies any links to Wahhabism or Uamsho although before a government ban, the station had given Uamsho preachers airtime.
The strategy is the same as it has been in countries like Pakistan, Mali, Somalia, and others; get them young, fill their minds with hate, and send them out to kill. To see this pattern repeated in a country like Zanzibar with the west standing by and doing little to prevent it, is a preventable tragedy. Washington's help is welcome, but much more needs to be done if we are going to head off another Islamist takeover.