Those airpumps probably differ in air output capacity. As tank volumes get bigger, the deeper water creates more pressure therefore needing for a stonger pump to be able to overcome the resistance. You might not need to upgrade. Just hook it up to your sponge filter and put in in your new tank. Its the bubbles that create a vacuum and draw water through the sponge. If the pump is able to push out a steady mass of bubbles then an upgrade wont be necessary.