Sounds like quite the group od mismatched tankmates. Well, I won't yell at you because anyone who has kept an aquarium has done the smae thing at least once, well likely a lot more. So, as long as you get a plan no worries.
Here is how I see it, the Silver Dollars, shark and at least one pleco need to go. Even if you just took one of these fish your tank would be a bit crowded. Some folks manage various plecos in tanks way too small for the fish size and do just fine. Are you one of those people? The gouramis will also get large 4"-8" and Kissers have a bad reputation for being mean. Your barbs are the fin nippy type and can hold their own with most non-cichlid tankmates. You need to ask yourself what is it that you want in your tank? Do you want a peaceful community? If so the fish you have don't work. Do you want a semi-aggressive community? The barbs and at least one gourami works. In that mix, the shark can hang with you until it reaches 3 1/2"-4" then it has to go. The sharks start off shy and non-aggressive. When they get big it is payback time.
So, figure out what you want and give the pet store back the stuff you don't want. Be thinking about fish that inhabit the top, middle and bottom. Once you thin the heard than you have time to think a bit more.
Here is how I see it, the Silver Dollars, shark and at least one pleco need to go. Even if you just took one of these fish your tank would be a bit crowded. Some folks manage various plecos in tanks way too small for the fish size and do just fine. Are you one of those people? The gouramis will also get large 4"-8" and Kissers have a bad reputation for being mean. Your barbs are the fin nippy type and can hold their own with most non-cichlid tankmates. You need to ask yourself what is it that you want in your tank? Do you want a peaceful community? If so the fish you have don't work. Do you want a semi-aggressive community? The barbs and at least one gourami works. In that mix, the shark can hang with you until it reaches 3 1/2"-4" then it has to go. The sharks start off shy and non-aggressive. When they get big it is payback time.
So, figure out what you want and give the pet store back the stuff you don't want. Be thinking about fish that inhabit the top, middle and bottom. Once you thin the heard than you have time to think a bit more.