Very interesting! And, yes, they are very hardy! I have one of mine for 6 years, and he's still going strong. But lately, he's been doing something totally strange to me; he turned completely dark, almost black! I haven't a clue why he does that! I'm suspecting it's mating season. He's been that color since spring. Either that or I have to feed him food that is high in beta-caratine. Anyway, cheers!