I hadn't realised before this thread came back from the dead that a seahorse could die. Certainly I've never seen seen any of mine with an infection, and that's the only way the fishes in Isola die - they don't die of old age. The sea horse also seems to be on a different timescale to the others; while I have several fish aged 9999, the seahorse is only in the low hundreds (I don't have FT on this machine so I can't check their exact ages).