Turning water pump on/off using Arduino Uno R3

I'm trying to build a simple system to turn a water pump every 24 hours for 10-20 seconds. I have 5V pump. When I connect it to 5V, GND it works but when I connect it to pin 12 (or any other digital pin) and GND it does not work. Here's my sample sketch:

int led = 12;


void setup() {                
  Serial.begin(9600);
  pinMode(led, OUTPUT);     
}

void loop() {
  digitalWrite(led, HIGH);
}

What am I doing wrong?