Switching Tank Size

[mirandaj]

If I am switching to a larger tank (75 gal), how long before I can transfer my fish from the 15 gallon. I have Strawberry, A Clown Fish, a damsel, Clown watchman goby, and should I buy all new gravel or can I use the gravel from the 20 gallon along with new? Should I buy all new live rock or what? I dont have any interest in buying new fish just yet either. I want to convert that tank to my breeding tank for my fancy guppies so its not going to be a salt water tank anymore...
:help:

 

[fishieness]

if you have gravel in the 20, then yes, i would switch to sand. Wait until your tank is all cycled and then wait about two weeks before adding your fist fish. Acclimate that one and every week or two add another one of your fish. Slowly add the live rock too.