2 were eating fine (frozen mysis) - one of those lasted a few weeks and then developed a lump on his side. He quit eating at this point and wasted away. The other that was eating developed a weird discoloration from his gills down the length of his jaw on one side of his face. This happened after a couple of days and then he died shortly thereafter. The other two picked at the rocks but never ate offered foods. This has been over the space of a couple years in 2 different tanks. Water params all looked good.

I've noticed a lot of folks here talking about keeping them with success and just wondered what the "trick" is.