You should send change to an address you own i.e. another address in your wallet. See here for more about change:
https://bitcoinspakistan.com/blog/all-about-change-and-change-addresses/
Topic: What are change addresses on blockchain? (Read 783 times)
'Change Addresses' are a rather confusing feature of the original bitcoin client. When bitcoin-qt sends coins it doesn't just send x number of coins but sends enough 'inputs' (chunks of coins you received) to fulfill your request to sent coins. The remainder from those inputs is sent to your 'change address'. Just send the change to the address your sending the coins from, or to another address you own.
Under custom send, should I specify the change address as the 1 and only address itself that I am sending bitcoins to? does this mean that if I had 12 bitcoins in my blockchain.info hot wallet and I wanted to send 5 bitcoins to a paper wallet address, the other 7 bitcoins go to a change wallet? 
Im really confused because I thought the amount of bitcoins you have goes untouched, why would they turn into "change"??
Im really confused because I thought the amount of bitcoins you have goes untouched, why would they turn into "change"?? Jump to: