im not sure if its the best but my background color is black and i have pool filter white sand for substrate. Ph is at 7.0 and temp is 85F. they are really active showing great color and eating like hogs 2-3 times a day
My PH is 6.4 water temp is 79.9 on average. They all do fine. I really dont think it matters as much as keeping the water clean and doing your water changes weekly.