RO/DI units. Kind of an iffy one. Some swear by it, others say they don't use it. Both seasoned and starters. The idea is to start with pure water so you actually know what you are adding to your tank, specially a lot of livestocks are sensitive to sertain chemicals or elements naturally found in most tap water and also some nutrients that promote nuisance growth, like algae, which you don't want in your tank.

Welcome to Canreef
check out under photo forum if you are not sure what kind of setup you interested in.
there is a big selection of setups.
do allot of reading on the ones you like under journals.
(which reminds me i need to make a journal of my own setup,lol)
do it slow as it will payoff with minimal over cost.

This is a research intensive hobby. Read, read and read.

This is an expensive hobby. Spend, spend and spend.

+1 on this advice. Take your time to read some of the documents by a few around here. Let your system take hold once you get your live rock placed in the tank. Depending which way you are going: Reef (takes longer) Fish Only (not as long).......but be careful and read about everything you add to your tank. Fish are something to research...once you get a couple...then you need to ensure you are adding compatable for your community. Have fun and look at the live rock closely when you start. Get a flashlight and watch the natural things found in live rock grow......you are at a very exciting time....don't let that hurry things too much. This is how people get into trouble. Ask any of us....PM if you like. This can help you very much. If you have any questions give someone on here a shout. Brad

for my 2 90 gallons, what start off lighting do you recommend? Tanks are 48 long...dont really want to upgrade often neither

Well, I would look into a 48" T5HO fixture, 6 bulb or 8 bulb or if you have around $3500 get a 48" LED fixture.

Now most new guys start with softies and LPS and zoos just because if you crash your tank most softies and LPS and zoos can survive through a crash if you are quick enough to stabalize your tank.

This all depends on what you're going to have in the tank. That is absolutely the first thing you need to decide.

I am also a newbie to salt and one thing that I have read is that it is good to follow the 12 month rule. You shouldnt add corals until the tank has been running for at least 12 months. Is this a general rule of thumb?

welcome to the board.
once you have done a bit of research into the hobby (by trial or fire) you will realize how general the questions you are asking are.

Many people here would love to help, but you need to so some basic research into this hobby and establish some expectations first...otherwise we can only offer advicebased on what our expectations are.

You don't need a dionizer. You might need a dehumidifier?

It isn't really a rule, but it does take a year for a tank to really mature. You can add corals on week two if you like, but as someone else suggested, if your tank crashes you could lose everything - and quickly. More important is the experience that comes with running the tank for a while. You would be surprised at how much there is to learn.

Some advice...

• Don't buy a chiller - use a fan for evaporative cooling
• Don't worry about Ozone or UV
• Consider biopellets or Zeovit, but not right away. Wait at least six months and read what the skeptics say before investing.
• Don't try to stock pile hardware - get the tank up and running and buy what you need.
• Don't under estimate the flow requirements
• Don't rely on your return pump for flow.
• Plan to experiment with a refegium, but not right away - it can wait.
• Buy what you really want now - don't plan to upgrade right away or you are just wasting your money on the first purchase.
• Big ticket items are the skimmer, lighting, live rock, live stock. This is where you will regret cutting corners.
• Be realistic about your budget.
• Google is your friend.