I am a great believer in providing the optimum water chemistry for each species. I feel that it is only by providing the ideal conditions can we expect fish to live out their full maximum lifespans in captivity. That is why it troubles me whenever I see an aquarium containing both livebearers and tetras because if the chemistry is right for one, it must be wrong for the other.
There are plenty of sources of information that list the ideal water conditions for each species. However, the one bit of information never included is the normal lifespan. I tried keeping male Siamese fighters in my aquarium on several occasions but discovered that they usually died after nine months to a year whilst many of the other fish in the tank have been in my care five years plus. I concluded that I was failing to provide the conditions that they require. It was only after a casual conversation with one of the dealers I frequent did I discover that Siamese fighters are a short lived species and twelve months is a “good innings”. If there is someone out there with more knowledge than me that could band fish species as either ephemeral, potentially long lived or permanent guests, I for one would find it most useful.