Marine Lighting - T5 lighting vs Metal halide
As mentioned in the overview there are many different options for marine lighting but it basically comes down to T5 or metal halide. From my experience T5 lighting seems to be the best value for money with the actual lights being cheaper than metal halide. They are also cheaper to run as generally it takes a lower watt rating T5 fixture to produce the same beneficial light as a much higher watt metal halide. This is based on the PAR rating of the two light fittings. Metal halides can also produce a lot more heat so may cause heating problems with your tank or require an additional cooling system. Having said all that it is my understanding metal halides will provide a slightly clearer lighting which is preferred by many enthusiast so like many aspects of reef keeping it could come down to cost. T8 is basically an older version of the T5, with the T5 being much smaller tubes that produce more powerful lighting.
This is mainly for my notes but T5 bulbs come in the following lamp variations
Another possible advantage of T5 or T8 lighting is that you might already have a one of these light fixings lying around as you may be upgrading an existing fresh water aquarium to your marine tank. This would then fit into the start as cheap as possible ethos, which involves using whatever equipment you already have or can get hold of cheap and then upgrading as you learn more and understand what it is you actually need. The alternative is the more costly option where you find someone you trust who has the knowledge to tell you what to buy. The danger of this method is that the information you get ends up being wrong and you end up upgrading it all anyway. You could also run the risk of never really fully understanding what you are doing and every time something goes wrong you are at the mercy of people who will be happy to sell you something you may not really need.