how come sometimes a fish is isolated in a cup in a tank

[pairenoid]

im just wondering because 2 gobys i bought, where both inside a cup with air holes, inside a bigger tank, and they both died. One i didnt acclimate good, the other i drip acclimated for 1 hour

Im just wondering if this is how most gobys are sold? im going to the store today and i remember seeing another in a cup, but im not sure if that means anything

 

[Beengirl]

Sometimes they'll isolate a fish for various reasons. One of my LFS always puts the snowflake eels in one of those critter keepers cuz they're escape artists. Sometimes they'll have mandarins in separate containers cuz they're training them to eat frozen. Sometimes fish are getting picked on and there aren't any appropriate tanks to put them in, so they'll put them in there. I would ask the LFS what their reason was if you want to know.

 

[obscurereef]

A lot of small gobies and inverts like sexy shrimp or small pistol shrimps will be in a cup. I'm pretty sure they do this b/c of how small the critters are and they could get sucked up in an overflow or hide/disappear. Your parameters might be a factor of why the gobies died. When an SW organism isn't acclimated properly or at all they will become shocked and can die, get disease, etc.