Can you ask the LFS where the Rainford came from? If it is from biota they should know that.
I have never seen my captive bred Rainford Goby eat. Yet right now she is in a Home Depot bucket doing TTM for ich and seems to be eating.
@Cessna89811 - does yours come to get food when you feed the tank? Is it picking food out of the water like the other fish or getting them from rocks and sand?
I have seen a thread on r2r where someone fed the Rainford Larry’s reef frenzy brand food and she ate it from the water column. That goby had not been eating and eventually died, but the LRF food did induce a feeding response.