I think you may be confused. Cannister filters don't require drilling. There is an intake pipe and outlet pipe going from the filter to the tank that attaches to the side using suction cups. I also recommend 2 cannister filters. I run an eheim 2217 on my 40 breeder, and it is barely enough.Nice.. i was thinking of getting two smaller filters that are for 40-50 gallon tanks rather than getting those huge external filters that require drilling and stuff. Is that what you meant by two filters? Seems cheapest and easiest to me.. just buy like two aquen or marine filters or something that cost like 40-50$ each or whatever lol..