I have a 45 gallon bow front tank that I want to change from a Malawi community tank to a Tangayika tank. Do I really have to put sand in it or can I just use the gravel that I already have? The gravel is black. I want to get about 6 trophous moori muzzles and a small school of Lupies. Is this a good pairing. I am getting some mixed opinions from some local aquarist. I have a 90 gallon Malawi setup in the basement. Also is having a power head really worth it?