if they want to be able to keep anything...I would suggest that they go with a halide set up from the start, at least I sure wished I would have...I would have saved a grip of "fun dollars" if I would have.
If there is no possibility of up grading to a bigger tank/deeper tank in the future...I would go with 175 watt halides and 2 x 110 watt VHO's. (yeah I have a few PC lights but I prefer VHO in no uncertain terms in most cases). 2 x 250 watt halides and VHO's if I thought I might go to a bigger or deeper tank in the somewhat near future, ie...75 gallons, 120 gallons etc.... If they like the blue look....then 2 x 250 halides with 14000k-20000k bulbs and 1 x 110 watt VHO day light and 1 x 110 watt VHO actinic. With the higher Kelvin rated bulbs you will need to go up in wattage in order to maintian intensity of light to the bottom of the tank. Another option is to just get 2 x 110 watt VHO's initially and have softies and what not and then as they progress to SPS and clams "add" the halides and take the plunge. Adding one halide at one end is not a bad idea and would allow for time to transition from a softie, SPS tank to a full on SPS/clam tank later with two halides. wrightme43 made another very valid point to consider to, the one about the lights possible taking up so much room over the top of the tank that HOB accessories may pose interference problems. Just another aspect to take into account before commiting...
The VHOs could be turned on to get the dawn and dusk light, and the halides could be cut on to simulate high noon so to speak. 175's are adequate for a 55 gallons tank depth, 250's are a few dollars more, and give you a lot more wattage for minimum fun dollars over the 175's, but yet are still in my opinion within the limits of sanity when it comes to lighting. You could put 400's on it but that would be pretty extreme over kill on a 55 gallon tank. Dont get me wrong there are some people that do that and they have nice tanks I just think there is a point where you reach a point of diminishing returns when it comes to lighting. And now that 1000 watt fixtures are available...well you get my point, but I am sure someone out there will do it sooner or later but then do you really need 2000+ watts of light on a 55 to keep corals?
My strongest recommendation is that they go and look at a number of tanks with different combinations of lighting and different corals and then decide what they like or dont like and then go from there. This will put things in a far more accurate perspective then just opinions on a forum alone, and less chance that they will make a choice that they later might regret. But dont get me wrong! Opinions are still very helpful to be sure!!!
HTH's a little without hurting someones feelings....
