I am adding a touch tank to the natural history musem with sea urchins and starfish. I'm not quite convinced that tropicraft mob spawning is fixed because I flew around for hours looking for starfish and urchins and finally benign server owner took pity on me and gave me some eggs. Still didn't see many other mobs either (but I do have some iguanas now from a giant tree spawner). At least the koa are now actively fishing and not just standing around.

However! Place starfish in tropics water, they take damage and die right away. Does anyone know what it takes to keep starfish alive in an aquarium?

In creative I have tried: different depths of water, different kinds of water (tropics, regular, on land) different substrate (sand, purified sand, dirt, stone). They seem to have a lifespan of about 20 seconds or so.