You get it from the ice knight on the ice planet.
the guy at the door fives it 2 you
You just aim and click. The only time it is effective is when it goes into the dragon's mouth when there are no flames there (you have to put it to sleep for a second or two). Climb around the back, dodge the spike ball, and pull the lever. (see related question)
Sir peleas gives it to you at the bottom of the volcano cave. (see related question)
On the Fire Planet, you get it from Sir Peleas when you reach the bottom of the interior of the volcano. (see related question)
jump from the rocks to rock then go in the valcano and watch out for the heavy sparks then to do the dragon jump chain to chain then pull the lever shoot the ice arrow in his mouth 3x done with fire planet
at these coordinates X:73 Y:83
There are no cubes on Astro Knights island. There are ice floes on the Ice Planet, that you jump across to avoid the robot fish.
The space sharks are surrounding the Ice Planet at X-73 Y-83, down and to the right from the planet Poptropica.
After you defeat the ice plant you go to the fire plant or jungle plant. But if you were already there you can go to the asteroid belt where there is a castle shaped like an asteroid.
The dragon can only be defeated by the Ice Arrow when the lever is pulled. His fire goes out and his mouth is open.
On Nabooti Island, the Mountains of the Moon have a snowy path to the top. On Astro Knights island, the Ice planet is one of the three planets to defeat.
If you travel from the Ice Planet to the Jungle Planet, you will fly across the sun in the Poptropica solar system. It is located at X-25 Y-42 and is apparently just decorative.