For future reference:
When you are transfering a sponge from the bag to tank, use a cup instead of pulling it out. After acclimation, take a cup full of your tank water and submerge it in the bag so that is is low enough that you can scoop the sponge into the cup without it hitting the air. After this, submerge the cup in your tank so that you can get the sponge into the tank without touching air as well. The problem is that air is quite harmful to a sponge and it can die from it, causing decay in your tank. Sponges are always good though, awesome find and good luck!