We had a very successful 75 gallon saltwater setup. In addition to what was said about (about Reef Central and local clubs especially) --- take your time! Live rock and live sand are your friends. Read about the right amounts and follow them. You will thank me later... Some people get really elaborate with their setups, and that is great, but some times the cost and time tinkering around with complex setup can be offset with some common sense and patience.
Unlike fresh water setups, I found that after about 18 months, our 75 gallon saltwater setup was MUCH easier to maintain than any 10/20 gallon freshwater setup we had ever had. The key? Remember that live sand and live rock? Yup. Real, LIVE filtration...
For live sand, you can start with even simple, clean playsand (the fine stuff) found at home improvement stores. I think that there is even a brand or product called "Play Sand". That is what you want. Put enough live rock in there, and the sand will eventually become "live" too. Better yet is to get some live sand from a local enthusiast to "seed" your live sand bed.
For live rock, if you get it local is *should* be a little bit better than shipping it in since the local stuff should have gone through a die-off from shipping already. If you have some shipped there are some great places online to get it, just search and you should find some decent deals. Just plan on a little longer "cycle" process, but that isn't a bad thing... Remember, we are taking this SLOW...
Anyway, on the live rock, there are different kinds. Some that stack nice, others are "branchy", etc. The key is that you want surface area so that more of the good stuff, like the awesome purple coralline algae, has a place to grow, and thus, more natural filtration.
Get 2 smaller heaters vs. 1 larger one. If one of them fails, at least there is some heat besides what comes from the lights.
For a 40 gallon setup, compact florescent is a good way to go. Unless you want to set up a bunch of corals later on (like YEARS later), stick with CF bulbs. A nice mix of daytime and actinic will work great. That said, you don't even need lights for a while. Remember, we are taking this slow, and during the first chunk of the cycle period, you don't need lights.
Water flow is key. Get a number of pumps, and some sort of mechanical filtration. A simple canister filter can do wonders, trust me.
Use any of the readily available salt mixes, and mix the water in the empty aquarium for your first "batch". Keep in mind that at this point, the tank should be just glass (or acrylic) with nothing else in it but water, salt, the heaters, and a couple of powerheads (water pumps), so don't fill it. You will be adding sand and rocks later. Check salinity after mixing it, and then again at least 1 day later to make sure things are in check.
After a day or two of looking at swirling water, go get and put in the live rock, sand (seeded from another tank if possible), any additional powerheads, and the filter.
LET THE SYSTEM START TO CYCLE. Do NOT add fish of any kind. Do NOT add inverts (snails, crabs, etc) at all for a couple of weeks at least!
Sprinkle in some fish food after a week to "feed" the rock and sand. Basically, you are starting to add a "bio-load" to the system so that it can handle fish waste later on. Do this for another couple of weeks if you can stand it. The longer you do this, the better the system will be for your first fish.
Ignore what pet shops say about "starter fish". Most "starter" fish are cheap and hearty, but can turn into absolute bullies in your tank later. Many times people put some sort of damsel in there, but they can grow large and be aggressive. Skip them. If you want a cheap, peaceful fish, look at some green or blue chromis. Better yet, it do the bio load for a couple of weeks with the fish food, and add something that you will possibly want later that is somewhat hearty, like a pair of small clownfish. Emphasis on small. Let them grow in the tank. Oh, at this point you should have those lights going and have been monitoring salinity, plus all of the basic water tests daily. After a couple of months, you will get down to a test a week, and after a year, you could be down to 1 serious test a month, and just some basic pH and salinity tests a week.
Again, GO SLOW! You will enjoy it a LOT better.
So now you have a tank with a couple of happy-go-lucky clownfish. In the whole tank. Happy as can be for a solid month. At this point, you could easily be at the 6 month mark before adding a 3rd fish. You could add some small snails at this point too. Be careful of "cleaner crew" packages online. Usually they are great for a large setup that has a number of fish in it. IF you put one of those in too soon, you will have too many mouths trying to eat fish waste... Snails will die off, or if there are little crabs, they will kill the snails for food, and the tiny hermits will also do it for their shells. Then you could have a bio-load spike that is too much for the rock/sand and lose the fish without serious water changes.
So with the cleanup crew, it is best to add a few as you go... What was that saying? TAKE IT SLOW.
Some of my favorite, low cost cleaners are Nassarius snails. I saw a ton of these on some of the murkier beaches in Florida the last time we were there. They cost like a buck a piece, stay small, and are quite hearty. We had a number of blue-legged hermits which start out small, but took out almost all of our snails, so we went "claw free" for a while. The tank (and snails) were happier for it. If you want a crab in there, get a little green crab or something that grows its own shell. Again, the snails will thank you.
Then the process is to slowly, one at a time, add other fish and wait several weeks at least between adding fish. With 40 gallons, you will be limited to smaller fish, but there are some cool ones out there. Firefish are neat, gobies can be cool (most tend to be bottom feeders, so limit them and make sure that there is plenty for them to eat), pigmy anglefish are cute. A flame angel is almost a must. Tangs will be too big, as will larger angelfish. With 40 gallons, you will only be able to have a small handful of fish, but it will be awesome!
I have so much more information, but my wife says that I should be either researching a senegal chameleon for my 12 year old for Christmas, or working in the basement. Either way, it isn't typing any more here... for now....
