How big is the CFL? Is that one of those fluorescent lights that screw into an incandecent socket? If so, you definitely need more light. For recovery it might be ok cuz you dont want to burn the coral while its week...but why was it dying? I'm assuming not lack of light because they'll show signs of that for months before they die. I'd say the bigger issue is making sure that everything as far as water params are in check.
But to answer the question, it will need more light in time. PC's at the very minimum, but leathers are my favorite and i've tried all sorts of things with them, and i've found that the brighter the better. They do great in the type of light that sps requires. I switched from pc to t5 and the difference was night and day with my leathers.
As far as changing water....IMO you dont want to do that too much with a dying coral if at all possible. Obviously if there is amonia and lots of nitrates and that sort of thing in there, you gotta do it...but if the water tests good, dont touch it. Stability is the name of the game with dying corals. Changing water all the time runs you the risk of altering something in the water, ESPECIALLY in that small of a tank....stuff can change fast there.
As far as filtration, you shouldnt need much being that its only one coral in there...the corals dont really add to the bioload, and dont really produce waste...i've gotten by with nothing other than sand in coral tanks, but a chunk of live rock might be beneficial. Make sure you've got good flow. Toads love higher flow, but be careful when its weak...wait till it starts recovering before you bump it up too much.
and no it shouldnt matter that its only 5 gallons...other than stuff can change fast in that little of water, so be careful like i said.
Sorry if that was a lot of typing...i tend to get sidetracked and type faster than i'm actually thinking lol
