Well I HAVE to put my two cents in on this one.
First for all of you that are using your soldering irons to poke holes in your tank, I sure hope your using some great ventilation since the fumes are toxic toxic toxic..
As far as using a drill bit goes, if cracking is a big problem dull your bit on the cement sometimes a very light tap with a hammer is necessary. I use the same technique for drilling in acrylic. It will cause more of the plastic to melt wich will prevent its from cracking as easy. With any project wich involves power tools remember safety first. Use protective equipment and TAKE YOUR TIME.
Snakes? I just like to teraform!