Choose the substitute based on your cooking method: flaky baking swaps first (cod/pollock/halibut), then gently rich swaps (trout/salmon), then non-fish (pressed tofu).
Match thickness: if your substitute is thicker than tilapia, add 2–4 minutes; if thinner, start checking 2 minutes early.
Bake or pan-cook until it flakes: target doneness at around 120–135°F (depending on thickness) and stop as soon as it separates into moist flakes.
If your recipe uses breading or a rub, keep the coating similar; for tofu, press first and bake on parchment to reduce sticking.
Taste-check and adjust: mild swaps benefit from extra lemon + salt/pepper, while fattier options may need less added oil.