Looks like it's $30 for 30 days at Selected YMCA Gyms at the moment
http://www.carltonbaths.ymca.org.au/ - Carlton Baths
http://www.kensington.ymca.org.au/ - Kensington Rec Centre
http://www.recwest.ymca.org.au/ - RecWest Footscray
And a number of others in their network. Not sure if this is just melbourne or nationwide: https://www.google.com.au/webhp?sourceid=chrome-instant&rlz=…
TIP: Call your insurer, if they cover gym memberships, you can get some of this back.
This is the same network of gyms as the Premier's active april.