Hmmmm, I too have heard and read that these cute little fish can only be kept in cooler water, but personally I have had great success keeping them in tropical waters as long as the temperature doesn't reach much over 78 degrees. I presently have 5 in my store right now. I have had these fish in the store for 3 months now. They are housed in a tank with a lot of calaurpa two red headed gobies and one baby bangaii cardinal. All the fish in this tank are getting along reasonably well, although the catalina gobies bicker amoung each other, I haven't seen any damage too their fins.
I am not sure if these are rare fish or not , but I rarely see them on our lists that I get from my suppliers.