To find the change in the amount of water removed in 1 minute, we need to calculate the rate at which the pump removes water.
The pump removes 250 gallons in 5 minutes, so the rate of removal is:
\[ \text{Rate} = \frac{250 \text{ gallons}}{5 \text{ minutes}} = 50 \text{ gallons per minute} \]
Since the pump is removing water, the change in the amount of water in the tank is negative. Therefore, the change in the amount of water in 1 minute is:
\[ -50 \text{ gallons} \]
So, the answer is \(-50\).