Switching From 5 Gallon To 30 Gallon.

[Ch4rlie]

Am afraid I agree that a comet goldfish has no place in a 5 gallon tank, the tank is too small and will undoubtly stunt the fish's growth.
 
A little more information for you regarding goldfish (which incidentally was written by fluttermoth )-
 
http/www.fishforums.net/index.php?/topic/417799-goldfish-for-beginners/
 
And yes, you can transfer ALL the media from the small filter to the C3 (I have a C3 filter btw so i know you can do this) one way or the other, cut the filter sponge if needs be, and add the ceramic / noodles etc.

 

[ScalpCrabs]

I decided to give the fish back to the pet store seeing as how it might take longer than expected for my friend to get the tank. 
Ive also started a cycle with ammonia. Thanks for all the advice. 
I have another question but on a different topic, so I'm going to start a new thread.