Need Help!!!!!!!

holy hell,,did you cycle the tank?? That sounds like poisoning to me, whether it be ammonia, nitrite, or chlorine chloramine.

www.skepticalaquarist.com thats my best answer

Yep--that's a lot of fish for a brand new tank. They produce waste (ammonia), which in mature tanks will be converted into nitrites and nitrates by bacteria. In a brand new tank, the bacteria aren't ready--not enough of them to deal with the quantity. These toxins build up, and impair the fishes ability to absorb oxygen.

If you can, take the fish back, read up on fishless cycling and fish species profiles, and start anew. If you can't take those fish back, you'll need to start doing daily water changes--and get some test kits. Ammonia and nitrites, pH to begin with, nitrates in a week or two. When ammonia or nitrites hit more than 1, do water changes. Once both of those are at 0, you can start doing watr changes less frequently. In between water changes, hang out here and read threads on fishy cycling, check into species profiles, learn more about keeping fish.

Oh yeah, and don't go buy more fish.

Welcome aboard!

What temp do you keep the tank at? Comets are Goldfish right? Goldfish are coldwater fish, shouldn't be kept with tropicals IMO, could they have been starved for oxygen in too warm of water?