Hey thanks for the input! I have always used several HOB filters on my tanks. I have 2 powerheads in the 125 but they just plug into the wall and do not use a sump. Truth be told I have never used a sump/ protien skimmer (are they the same thing)? and have no idea how they work. (I was thinking about using the 55 as a sump below the 125 when I got to it) As for the 29 could you post a link to a light that would work (I intend to have soft corals for the clown fish enenimies or whatever they are called ha. Also will my HOB filter be sufficient for the 29?
Here goes...
Start by doing a lot a lot a lot of reading! Then keep reading! Research beforehand will save tons of money and headaches.
You can do what bigcountry said, but you need to slow down the time frame a lot. Remove everything from the tank and clean it. Then get some sand and put it on the bottom. I would highly recommend getting some rock. It looks natural and helps with filtration. You can get dry rock and it will become "live" to save some money compared to the high prices on "live" rock. Live Rock means that bacteria have grown on and in it. This bacteria help break down waste just like freshwater tanks(ammonia to nitrite to nitrate). Get a hydrometer, salt, and Prime declorinator. Mix up a batch of water and fill the tank. You can add the rock before or after. Once full turn on your filters. You NEED powerheads or other water movement. The salt takes up a lot of the holding capacity of water and the oxygen levels are lower, so you need the water to be moving as much as possible(particularly on the surface) to keep it oxygenated. Once everything is in place let everything run for a couple WEEKS. During this time you can test your ammonia, nitrite, nitrate to see how the cycle is going. Once you have no ammonia or nitrite and some nitrates you can add ONE fish. Go slow in stocking, overstocking quickly can cause a number of problems, including ammonia because the bacterial filtration can't keep up. After you keep that fish alive for a while(weeks to month(s)) and you have everything stable you can add another fish and so on.
You can NOT have a tang in anything smaller than a 75 or so(I feel even bigger and most tangs need more like a 210 long term). The clowns would be a good idea. Same with a shrimp, some hermit crabs, and snails. Little gobies or a damsel or chromis work as well.(the damsel or chromis should probably go fish, then the 2 clowns at the same time).
If you upgrade your lighting, in a few months you could start keeping some very hardy mushrooms or soft corals. Then after keeping them alive and growing you can move on to some LPS and SPS once you upgrade your filtration(skimmer, probably sump, etc.)
A sump is basically a container generally below your tank that you flow water into. It will hold your filtration like skimmer, heaters, etc. Water will flow through it and get "filtered" and then be pumped back to the tank.
A skimmer is a protein skimmer. It is an acrylic piece of equipment that needs a dedicated pump. The pump will water into the skimmer and add air in some way(venturi, injection, etc.) causing foam to be created. Wastes attach to this foam and the foam overflows into a cup where you would remove it. Skimmers are the best piece of filtration equipment you can buy. They help keep water clean and oxygenated. The only thing more inportant in my opinion is rock.
Keeping asking questions and reading. There is a lot to learn to be successful. Just don't go too fast!