I had a hermit in my big tank for 1week,decided it was killing everything so I moved it to a 7 gal live rock tank. While looking at my crab to feed it a small white and red fish came out and shot back in. It swim inside the shell of the crab and even changes shells with it. It is very small half the size of lets say a scianochromis cichlid hatchling.
Got the crab 3 weeks ago and it has just come in from the wild.The fish moves alot like a cleaner wrass or goby,,,upside down.
Ive put mesh on the intakes in case.
What could this be????
Thank you in advance