My tank is 36 inches

Fish only or reef? If fish only, flourescent or compact flourescent (CF) lighting is fine. If reef, CF lights at the least, and that's if were talking about soft corals and non-LPS and SPS corals. Check out the lighting options that CoraLife and MarineLand sell. Great products

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When in doubt, do a water change.

and if you want to go LPS or SPS you looking more twords t5 high output or the best option MH. But with better light comes a larger bill.

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What is the minimum number of watts I need?

I want to keep coral in the tank

WPG is an outdated term and doesnt work due to the different types of lighting available. What are the demensions of the tank as in LxWxH and keep in mind what you want your tank to look like down the road because it can be very expensive to buy the wrong lights and then buy the correct lights later.

36" x 18" x 16" is my tank size

I would say that 4 T-5's would give you plenty of light for most anything you might want.

I agree with the whole "WPG" being a bit outdated HOWEVER its always a good measurement to say I have X amount of watts per Y gallons.

For example I have 800watts of MH on a 150 giving me about 5 watts per gallon. However you also need to take into account what kelvin rating you are using. For example I use 20,000k which for SPS and LPS doesent really promote growth, however promotes great color. 14k promotes better growth but a little less color.

Its all in the light/kelvin rating.

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For t5 fixture I can put any t5 bulb in it as long as it is 4 bulbs

Make sure they are HO T-5's bulbs and fixture and I like Giesmann, ATI and UVL's.I am adding a link for you and you can go in an check out bulbs and there PAR readings.

home (tfivetesting)

Lighting can be a very personal thing. My suggestion is to look at as many operating systems as you can before buying. Find a LFS that has multiple tanks lit with different types of lighting, PC, VHO, T5, MH, LED or combinations of these. Some people like more blue, others more purple and yet others more white, they all have their place and all will grow corals and fish.
Lighting is a big investment and you would prefer do do it only once if possible. Some such as MH and T5 are very dependent on the reflectors for best performance. VHO can have internal reflectors but are not as efficient. LED is a new technology and is really gaining popularity. PC as well as VHO are old technology but still work for many people. Look not only at the type of bulbs and reflectors but at the color temperatures and light penetration. White lighting can look very washed out but may grow corals like weeds such as the XM 10k MH bulbs do, its best to supplement them with actinics such as VHO or T5 for best appearance. T5 by itself has gained ground in the past few years but I prefer the coloration of MH with VHO actinics, other will disagree. There is no right or wrong, and a lot of personal preference so find some LFS and even local club members who will let you take a look at their systems until you decide what suits your wants and needs.

Don't hurry into it.

I am just going to throw my 2 cents in on top of this already great advice. Try to think far in to the future. For example if you ever plan of having "high-end" not meaning expensive but LPS or SPS corals, you will probably want to go ahead and get the ligths that are made for that now. I know personally I would love to have MH because of the lighting effect they give on the bottom of the tank, thats the only reason I want them right now. I personally run the GLO HO T5 fixture and love it to death. In my research they cant be beat when compaired, as far as output goes, to other similar fixtures on the market.

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It has become more than a hobby! My 29gal Dream Reef DIY Build

HUGE vouch for GLO t5 i've got two of em and they are for sure one of my favorites, just don't have a tank for them yet.

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i have a 24 in running on my 90; i put all my coral on one side just so i could use it.

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It has become more than a hobby! My 29gal Dream Reef DIY Build