I almost always see them at Blue Sierra in Issaquah.
Ever check Fairwood Pets?, They actually have quite a selection of fish. Staff knowledge is little to none. Wasn't too happy last time I was in there though. They had "painted" fish in one tank. I asked if they knew these fish were injected to get the colors. The manager wasn't there and the young gal working was like, "oh wow, that seems odd, they sure sell fast".