I have 2 tiny baby green tree frogs in a small tank its 25cmx28cm and 18cm in height I currently have a heat lamp on them but I was thinking about getting a heat mat instead off ebay so I can move my frogs into my room because I can't sleep a light.

Is using a heat mat ok? Should I get one smaller or bigger than my tank? Because its such a small tank will it overheat?

I was looking at these ones
http://cgi.ebay.com.au/GNF-103-Repti...item27b0562bfa

http://cgi.ebay.com.au/Reptile-Snake...item414fa0272c

http://cgi.ebay.com.au/GNF-102-Repti...item2a05ae1f99

http://cgi.ebay.com.au/New-Heat-Mat-...item20afd7c68f