I have a medium size aquarium. Initially I bought 2 angel fish with few goldfishes. Suddenly the goldfishes keeps dying without any symptoms. I replaced few times, but it keeps dying. Also I noticed few dyed with few hours only after getting by swim bladder. Then I stop putting the goldfish in the tank and leave the 2 angels. Within 2-3 days one of the angel also died. Now there is only one angel which seems to be healthy. Please suggest what went wrong? My oxygen pump and filter is working OK, though I am not using any under water plantation. Is it the angel which is killing others? Should I keep only goldfish without angels? I am a novice in this, experts please suggest. Please..

Following your inquiry and not being an expert on gold fish, dip, I found this website called goldfish emergency 911 that explains all you need to know to have healthy goldfish. I do think vegetation is necessary for their health though.

GoldFish Emergency 911 - Goldfish, Back to Nature (http://www.goldfish-emergency.com/viewpage.php?page_id=246)