Regarding water after fish (I am new here and didn’t notice a response, See Moed Katan 11a Rashi and Tosfos. The R’ Akiva Eiger is in the Chidushei RA”E on Y”D 116:5, also see Oruch Hashulchon 116:10, Kaf Hachayim O”C 170 ois 79, brought also in the Kessef Mishneh Hil. Deios 4:18, also see Shorim Hamtzuonim bHalacha 33:2, (taken from the Sefer Shmiras haGuf v’haNefesh 1:19).