LOL welcome to the world of Marine, where nobody can ever 100% agree on anything
Basically lighting is a pretty hotly debated subject and there really is no "best" lighting solution. Currently there are 3 main options for lighting a reef tank (there are alternatives but I wont go into them here
). These are T5, Metal halide and high output LED's all have pros and cons. When looking at lighting you need to consider what spectrum they are capable of (this is the 6500k, 15000k stuff, 6500k gives a yellow light up to 20000k which is a very blue light).
T5 Pro's:
* Equipment costs are cheaper initially.
* You can mix and match tubes with different light spectrum's to get the desired colour in your tank.
* Lots of choice in core equipment and tubes.
* You can keep soft corals and LPS corals with ease. You can also keep SPS corals and high light requiring inverts as well but you will need more tubes (6+ and the costs gets prohibitive).
T5 Cons:
*They get hot (though nowhere near as hot as Metal halides.
*Tubes need replacing every 6 months and cost as lot.
*When using to light high light demanding critters (SPS, clam's, etc) you need a lot of tubes which means higher electric bills (and more tubes to replace).
Metal Halide Pros:
* Very high light output (two 150w MH units would take a lot of T5 tubes to beat it).
* Tubes only need replacing every 12 months so cheaper in that regard.
* Better water penetration. As light goes through water the usable light gets less, Metal halides are very good at getting high amounts of light even to the bottom of the tank (better then T5 and LED).
* More choice of corals and clams that require very high light output.
Metal Halide Cons:
* Initial cost is expensive. Despite what people have said here just getting a floodlight from your local hardware store and sticking a marine bulb in wont work.
* They get hot, very, very hot. This heat goes into the water and can cause the tank to over heat. If you live somewhere hot already then you are going to have to buy a chiller as well to cool the water.
* You don't have much control over the colour output in the tank. You have a range of tubes you can use (10000k, etc) but as you only have 1 or 2 tubes you cant mix and match them like T5's. Often you have T5 or T8 tubes along side them with Actinic tubes (Blue tubes, don't give much usable light but takes away the yellow from the Metal halide tubes).
* Some corals don't like MH lighting (a lot of LPS for example) so you need to take extra care in placement of these so they don't get "burnt". In general though it gives you more choice of corals and inverts.
* Metal halide units aren't very energy efficient and use the most electric out of all 3 light units. If you get an older unit these are even worse for high electric bills.
LED Pro's:
* Do not generate a lot of heat and the heat that is generated is directed away from the tank.
* Lower electricity costs.
* Similar output to T5 Lighting.
* Can be programmed for cool sunrise/sunset effects.
* Bulbs last up to 10 years so no replacement parts costs
* Gives a nice "shimmer" effect in the tank (same as Metal halides) that T5 cant give.
LED Con's
* Its REALLY, REALLY expensive to buy the kit. a 4x2x2 tank needs at least 8 of the TMC aquabeam 500 units at £100 each. And this still only gives about the same light output as the T5 unit that you linked above. You could say that the lower electrical costs and not needing to replace the bulbs will balance it out over time but for me I don't have £1000 to spend on lighting my tank right now so would prefer the cheaper solution that might cost a little be more over time.
* Its still a new technology. Some commercial LED units are rubbish and there isn't much of a second hand market for them yet so generally only the rubbish units come up for second hand purchasing.
Personally I use 6 T5 tubes with a mix of 6500k, 10000k and Actinic tubes. Soft corals and LPS have done fine under this but I haven't tried SPS yet (because I have had phosphate and water quality issues). Once my phosphates are sorted though I will be trying SPS with them and I do know people that have beautiful SPS tanks using only T5 lights (Morri is one) so it is possible.
I do plan to add some DIY LED units to my setup. Not to replace the T5's but to give me one or two high light spots in the tank (for clams and Nem's) as well as giving me the shimmer effect in the water (and so I can program them with a sunrise/sunset). this wont be until I have the money and time to put it together though.
/www.reefshops.com/lighting/t5-t5ho-flourescent/
