Mix the orange juice, lime juice, olive oil, cumin, and salt in a bowl and combine well.
Gently place the pieces of Tilapia into a large Ziploc bag and pour in the juice. Marinate for 2-4 hours in the refrigerator, flipping the bag over about halfway through.
Next, heat the olive oil over a large skillet. When the pan is warm, add the Tilapia and cook for about 4-5 minutes on 1 side, then turning only once, finish cooking on the other side (about 8-9 minutes total) or until it's cooked through to an internal temperature of 165F or 74C degrees.
Then, simply prepare your tacos to your liking using lettuce or soft/hard taco shells, add the fish, red pepper, onion, mango, and avocado.
Notes:
Quick Tip
Use your favorite toppings like cabbage slaw, radishes, tomatoes, etc.