I will have to respectfully disagree with Crispy. All of your preferences(focal point, no breeding, nice colors, and generally more peaceful) scream of an all male Hap/Peacock tank. I guarantee guests will think it's a salt water tank. It will be pricier, unless you buy smaller known males. Fully colored adult males are usually more $. In a 125, you'll have plenty of options. You won't need too much holey rock, as they prefer more open water, but you should provide at least a few safe havens for those that may need to seek it. The holes in the holey rock may not be big enough. If you do go this route, try to choose species that do not look similar, as this can cause possible conspecific aggression issues. Do your research and pick hap species that are lower on the aggression scale. Come up with a list and post it for opinion, there are plenty here that can help. Depending on species' you choose and their adult size, you can probably house upwards of 20 fish when all is said and done.