You can please edit your question and tell us what fish it is and it's weight so we may advise you properly.
Some fish bake for 15 minutes while others can take 30-40.
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Tilapia is a fine and tender fish.
Oven at 350, season your fish lightly with S&P, some olive oil and bake for 25-30 minutes.
When done, squeeze some fresh lemon on it and a final drizzle of olive oil.