Posiedon Aquatics IMO isn't that great. They have a very small selection of corals and most aren't that healthy, but by all means if you have the time why not stop. Seahorse is a must see. It is on Rt 8 in Allison Park just north of the city. Very nice set-up and selection. Another nice place is Atlantis which is south/west of the city on Rt 51. And if you have more time to kill further west about 15 miles is West Hills Pet Shop he is trying to expand his selection last time I was there he had some nice stuff, take 276 towards the Airport and get off in Moon Township and head towards Robert Morris University. The Plaza it is located in sits down in a little valley next to an off track betting place. You'll need to turn on to Broadhead Rd to get into the plaza. You should be able to get directions and actual addresses on the web.