I don't know where you are Vanwingen so don't know what type of fish you might be using. I cook fish for a living and find that any of our fish can be fried together in the same vat as long as you are not frying battered beside crumbed. Once the fish is coated the flavour will not depart the fish to any great extent but what is in the coating will. For example, if you use lemon pepper in your batter it will polute the oil after awhile and everything else will taste of lemon pepper.
I steer clear of any spicy foods simply because I have respect for my oils. Fish, chips, chicken = fine. Crumbed steak etc. = no. I work my oils down the line, I have 5 x 25ltr vats side by side, #1 [the freshest oil] for battered fish, #2 & 3 for chips, #4 for crumbing #5 for anything spicy, then out the door it goes.