From Daas Torah - translation copyrighted
Aruch HaShulchan (Y.D. 87:15): ... Both fish and grasshoppers are not prohibited to be eaten together with milk – even rabbinically. It is clear that it is permitted to cook fish together with milk and eat the combination. In fact is the established practice in all Jewish communities to do. However you should be aware that there is a textual error that occured in the great halachic work, the Beis Yosef, which mistakenly states that one should not eat fish and milk together because it is dangerous (Orech Chaim 173:2). There the Beis Yosef had in fact intended to mention that meat and milk is dangerous together (not fish and milk). This textual error has already been pointed out by the Rema in Darchei Moshe. However some authorities wish to rule according to this error because they say that in fact in medical books it states that fish and milk are an unhealthy combination. But in fact that is not so, because Rabbeinu Bachye writes in his commentary to Mishpatim that the danger is eating fish together with cheese because it causes leprosy – and not fish and milk. Furthermore if fish and milk were dangerous than why wasn’t this mentioned in the Shulchan Aruch? Furthermore the whole world eats fish and milk and it is considered a quality meal. There is fact is no one who is concerned for this and it is possible to eat them together without any concern. [See Tosfos at the end of the first chapter of Mo’ed Koton]
