I don't know, as I don't keep them. But as they are all wild caught they have a difficult time acclimating to tank conditions. Also, I have read that they have fairly "unusual" native parameters of a very high pH (over 8) wth a very low hardness which could be difficult to duplicate. I am not sure if this is intirely factual, but the consensus is that its not uncommon to have a large die off rate.