@jaghillam. I think the reason many of the most colorful fish colour up more in murky water probably goes back to natural habits they come .from.In the Amazon blackwaters Cardinals for example inhabit water very dark,theory is the bright colours are used to recognise the safety from predators in the shoal.Setting up a truly correct biotope would mainly consist of tangles of wood and leaves with rich tannined water,they would love it but we prefer to see them in crystal clear water planted tanks