No installation candidate for compiz

I tried to install 3d effect on my Debian Wheezy using command $ apt-get install compiz compizconfig-settings-manager compiz-fusion-plugins-main compiz-gnome compiz-gtk But it gives the following Reading package lists... Done Building dependency tree Reading state information... Done Package compiz is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source E: Package 'compiz' has no installation candidate E: Unable to locate package compizconfig-settings-manager E: Unable to locate package compiz-fusion-plugins-main E: Unable to locate package compiz-gnome E: Unable to locate package compiz-gtk What should I do now?