Thanks for your query. I do understand your concern regarding an antibiotic being prescribed for a fungal infection
of the ear. In most probability, you would have developed an inflammation of the ear canal
along with the fungal infection. Your ENT doctor has seen that and hence decided to treat you for the same. Coming to the other question, most medicines do induce acidity and hence an anatacid is prescribed with an antibiotic. Hope this helps.
Fungal infections can recur and do need prolonged cleaning and antifungal ear drops. To avoid recurrence, I would also suggest you to keep your ears absolutely dry, as moisture can cause fungal infections. Do not use ear buds. Wish you good health.