Fish gasping for air!! please help!!!

if ur fish are gasping at the surface its most likely not because they aren't getting enough oxygen, rather they are trying to escape contaminants in your water supply...
 
When replacing filter sponges, only replace ONE at a time!
 
Chaning the media in a filter should cause too big of a problem if the tank is stocked at a low to medium level, and especially if it has lots of rocks and decorations or plants. But if the tank is heavily to overstocked then it can lead to a bit of a mini cycle again.

Adding Stress Zyme won't hurt your tank but water changes usually work just as well.
 
Stress-zyme is only water conditioner. IMO it's a waste of money, there are WAY better water conditioners out there. The only thing that will help you is water changes.
 
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