Specific questions about retrofitting with existing equipment

[Chihuahua6]

I had a 90 gallon with two 175 watt single ended halides and two actinics. I want to use the existing stuff to build a hood for my 47 gal tall which is 20"X18" length and width. I had two ballasts but one is no longer working (melted near the cord). My husband put the old hood together by transferring it from another hood and that was two years ago so we don't know exactly how it works. Here's my stupid question. Does each halide bulb need a ballast or was one for the halides and one for the actinics? I only need one halide for the new tank so I was thinking I could use the socket and ballast, get another reflector that is smaller (or cut to fit) and retrofit it to the new hood. What about the actinics though? Do I buy a kit to add those to this hood? The old ones would obviously be too long. I am trying to save money by using what I have so any suggestions would be appreciated.