Well done LV. Your male guppy tank gives us a hint or two for many fish keepers.
An all male tank can be beautiful and not cause any problems.
A fairly high density guppy tank can be maintained with no real problems.
Your 15 year colony has produced a nice selection of fish without any particular controls to prevent "inbreeding" and has fish that are thriving, not weak and suffering from it.
We often see in-breeding blamed for a host of ills but your fish remind us that it is pure BS to place the blame there.