Can We Eat Fish and Milk Together in Islam?
Question

Did Muhammad (peace and blessings of Allah be upon him) ever teach people not to eat Fish and Milk together?
Praise be to Allah.It was not narrated that the Prophet (peace and blessings of Allah be upon him) forbade drinking milk at the same time as eating fish.
Since no such thing has been proven, then we should refer to the doctors concerning this issue. If they say that eating these things together is harmful, then they should not be eaten together, rather they should be eaten separately. But if there is no harm in eating them together, then you may do so if you wish.
It may be that eating them together is harmful for some people, because of individual sensitivities or allergies, or the nature of their bodies, whilst it is not harmful to others.
In conclusion, this matter should be referred to the experts.
For more details, please see the following answers:
Ruling on eating certain foods only in Ramadan
Can Muslims Eat Kosher?
Ruling on eating fish that fed on dead animals in artificial ponds
Ruling on Vitamin D3 derived from animal sources
Can We Eat Meat in al-Muharram?
And Allah knows best.