Tilapia

Tilapia keeps 1–3 days refrigerated and 6–8 months frozen as a lean fish. Store it cold and covered, on ice if you can manage it.

Almost all tilapia is farmed, and the great majority reaches US stores frozen. The fillets at the counter have usually been thawed from block-frozen product, often that morning, so they should not be refrozen — and the frozen bag in the same store is frequently the better purchase, since you control when the clock starts.

Tilapia fillets are thin and uniform, which means they thaw in under an hour in the refrigerator and overcook in about ninety seconds of inattention. Thaw in the fridge, never on the counter.

Pat fillets dry before storing. Farmed fish arrives wetter than wild, and standing moisture is what accelerates surface bacteria.

Tilapia is a lean freshwater fish, and both halves of that description matter.

Being lean — around two percent fat — means very little oxidative rancidity, which is why the freezer window runs to 6–8 months. Being freshwater means its spoilage smell is different from saltwater fish. Freshwater species carry much less trimethylamine oxide, so they produce less of the sharp ammoniac note that marine fish develop. Tilapia going off instead smells muddy, sour, or vaguely earthy.

That difference is worth knowing because it defeats the usual test. People expect spoiled fish to smell aggressively fishy; tilapia does not, and can be well past its window while smelling only faintly stale. Rely on the date and on texture rather than on your nose.

The "muddy" flavor tilapia is sometimes criticized for is a separate issue entirely, caused by geosmin from algae in the pond water. It is a farming and water-quality matter, present from day one, and it says nothing about freshness.

Discard on slimy surface, flesh that stays dented, or any sour smell.