Crystal fish (scientific name Placodermis Krystalla) are a life form found on any Sector Prime planet where volcanic activity is present. Existing in a tenuous balance between evolution and annihilation, these delicate aquatic creatures inhabit hot springs and sulphur fumaroles. They grow to about thirty centimeters in length.
Crystal fish can apparently see, but how or what they see through the two gold metallic orbs they possess is anyone's guess. Their reactions to other forms of stimuli besides light cannot easily be discerned - with the exception noted below.
Crystal fish are filter feeders. They literally breathe hot water, which passes into their mouths, through their bodies and out again, exiting through its gills, which appear to be its spindly crystal fins. Minerals, bacteria and other microorganisms are absorbed into its body in this way, replenishing and sustaining it, if in a very slow manner.
Crystal fish can survive for extremely long periods of time outside of their usual aquatic environment. Water at normal or cold temperatures simply slow the Crystal fish's already lethargic metabolism down a notch or two. It can even be frozen and then miraculously revived years later. Crystal fish are inactive out of water and go brittle and dormant within minutes of leaving their boiling environment. Many of them are displayed in museums in this form, and are highly sought after by art dealers and wealthy collectors.
Crystal fish live solitary lives and do not reproduce. They form, so to speak, by a rare, complex and not wholly understood process dependent upon the amount of raw minerals and exotic microorganisms present within a seemingly inhospitable underwater environment. Their life span is indefinite and they have no natural predators.