The only decent Petland Discounts that I've found that sells some coral, saltwater fish and live rock is the one that's on 50th and 9th. Their prices are a little more expensive than the Petco in Union Square, but sometimes they have some good stuff - SOMETIMES. I've gone there at times where their coral tank is a big mess, and I think that the employees have no idea what's going on - other times I've gone and it was beautiful, with huge pieces of frogspawn and sun corals. Pretty much hit or miss. The Petco in Union Square has a bunch of saltwater fish and inverts - they have some good stock sometimes, but if the fish has been there for more than a few days ick occasionally shows up (if you pick it up day of delivery, either Wed/Fri, chances are you'll get a healthy fish - I got a purple firefish the other day and it's doing great, starting eating the first night I brought it back home - they also got scissortails which were pretty cute). They also have a coral tank that IMO is a mess most of the time, aptasia everywhere, but sometimes they have some good polyp colonies, small clams, xenia, and mushrooms... little to no LPS, and never SPS.