You'd want to go with 96w PC on a 3' tank since the bulbs are 3' long, a 55w bulb is 2' long. I'd be tempted to go with all florescent bulbs on a tank that size, with MH you're probably gonna have heat problems especially if you don't have a sump. Your tank is very shallow so if you went with PC's only you'd still get good light penetration. A MH bulb only covers 2' well so you're gonna have less lit portions on the ends of the tank. I'd go with 3 or 4 96w PC's. Your dad's lights are probably only normal output and won't cut it for a reef tank but you could check the ballast and see what it runs.