The integrated stove cooks steamed fish for a few minutes, usually not more than fifteen minutes. How long it takes to steam bass in a steamer at 95 degrees depends on the size of bass. A kilo of perch usually takes about 12 minutes, and the longest is no more than 15 minutes. If the bigger one is properly extended for 3 to 5 minutes, the easiest way to judge is to see that the fish is familiar when it falls out of the fish's eye. According to the size of perch, a kilo of perch is generally about 12, and the longest is not more than 15. If the bigger one is properly extended for 3 to 5 minutes, the easiest way to judge is to see that the fish is familiar when it falls out of the fish's eye.