How much water do you take out of a 55email gallon tank if need to change 20 percent?

To calculate the amount of water you need to remove from a 55-gallon tank if you want to change 20%, simply multiply the total volume of the tank by the percentage you want to remove.

Amount of water to remove = 55 gallons * 20% = 11 gallons.

Therefore, you would need to remove 11 gallons of water from the 55-gallon tank to change 20% of the water.