It isn't necessary to drill tanks for bulkheads, although it is my preference. The only reason you would need to drill a tank is if you intend to use a sump or refugium to house a skimmer and/or macro algae (respectively). I highly recommend a sump or refugium, as it will add extra water to the total volume of the tank. More water means better stability. That said, there are other options if you choose to, or not to, use a sump or refugium. There are overflows that can be mounted to the tank which use a siphon to carry the water over the side of the tank, and there are hang on back (HOB) skimmers and refugiums that can be mounted on the back of the tank. The advantage of drilling the tank and using bulkheads is that it takes less space, and IMO, looks neater. All you can see are the (preferably two - one in each back corner) bulkheads and tubes that carry the water down to the sump/refugium. As far as return line(s), the same applies. You can use a "U" , which hangs over the back of the tank with a splitter or flare to return the water. Again, I prefer it to be drilled, as it looks neater. It's easy to drill a tank. You just need to know what size bulkheads you are going to use, and buy an inexpensive diamond dust hole saw. Water to keep the saw and glass cool, and an electric drill (cordless highly recommended). I've drilled several tanks, but as with anything pertaining to glass, there's always a risk of trashing your tank... but slow and careful drilling will result in success every time. There are several option available, but it all boils down to what you want.
