A sump is another tank that is connected to the main tank. You usually keep it under the stand, or somewhere out of site, but nothing is set in stone as to where you have to keep the sump. Whatever works for you is the best route to go. If the tank is tempered then yeah, don't drill it. You will need a HOB overflow. Look around the online retailers for the overflows. For a 55G tank you could get away with a 1" bulkhead.. which would be 600GPH.. but i know some people like more flow in their tanks, so i guess you could go bigger. It's up to you.
If you look at our "vendors" link, you will find a lot of places that sell SW equipment, and that's where you should start looking. If it's too pricey, try ebay or craigslist.
A HOB protein skimmer is a protein skimmer that just sits on the back of the tank.. sortof like one of those filters you normally see on freshwater tanks that run carbon and what not. The canister filter is a filter that has two tubes, one that sucks water from the tank and another that pushes it back in to the tank. These are normally used on freshwater tanks as well, but i'm beginning to see more and more of these canister filters being used in SW tanks. It's really all up to what you want to do, and what your money budget permits.. but in all honesty, i would say go with the overflow box and the sump. A 35G sump would be perfect. You could mod the 35G tank to make it a sump/refugium. And the sump is where you keep all of your heaters, skimmers, filters, reactors, etc.. if you have any, so you don't have to keep them in the main tank. Plus, you can do your top-offs in the sump instead of the main tank.
And the benefit of having a refugium in there, is that you can fill it up with tons of macro algae and other critters in which the macro algae will help keep your nitrates and phosphates to virtually zero, after some time of course, and the critters in the fuge will help break down detritus and other waste that may come from the main tank. It's really a whole awesome process and the benefits are endless on sump/fuge.. IMO.
Ok now as for the plumbing.. it really is simple so i won't drag it out at all. You're going to need the HOB overflow box, some clear or black vinyl flex tubing, and then you will need a return pump. You need to connect the tubing to the bulkhead on the HOB overflow, and that is the piece that will suck up water from the tank to bring it down to the sump. One thing you should do is ask more experienced people about a siphon break because i have no clue how one would work on a HOB overflow. You will need a siphon break in the event that your return pump shuts off, your overflow won't continuously drain water from the tank, because that would result in an overflow of your sump, and very wet floors.
Next, lets talk about the return pump because that is very essential in this whole sump business. You need to calculate the length from the sump, to the rim of the tank, because the return pump you get needs to push the water all the way up and back in to your tank. So if it's 6 feet from the bottom of the sump to the top of your tank, you will need a pump that can push water 6 feet up, and then some. If it's 6 feet.. you don't just want a pump that can push it only 6 ft because then you will have hardly any flow coming out of it. I was just using 6 feet as an example, so you will need to correctly calculate the length as i said before, and then report back to us so we can tell you what pump would be sufficient for your application.
So.. once it's all said and done and you have the return pump that works best for your application, you then take tubing SEPERATE from the overflow tubing, and then connect it to that pump. Then, you should get to 90degree PVC elbows, and have those PVC elbows go over the rim of your tank. This will be your return setup.
So basically, you will have the HOB overflow which drains in to the sump, and then the return pump which pushes the water back in to your tank. It's pretty simple, but i'll see if i can find an article on it, just incase i rambled more than i made sense.
Alright well here's a good article you should read on refugiums, since i mentioned putting one in your sump, which would be a very good idea.
http://www.aquariumadvice.com/articles/articles/21/1/Refugiumsfuges-or-refuge/Page1.html
AND for better information.. and hopefully for clarification if i rambled.. here's an article on sumps.
http://www.aquariumadvice.com/articles/articles/4/1/Sumps-Explained/Page1.html
Oh an dude.. please.. cycle your tank correctly this time around, please. It may take a little while, maybe it won't, but what we do know is that it will save you tons of money in the end, and will save your fish from meeting their deaths prematurely.
http://www.aquariumadvice.com/articles/articles/3/1/Cycle-your-salt-tank/Page1.html
