it sounds like you did not cycle your tank
cycling refers to the nitrogen cycle:
ammonia eating bacteria create nitrites
nitrite eating bacteria then covert the nitrites to nitrAtes
ammonia and nitrites should be 0
nitrAtes should be kept under 30 or 40 i think
this takes SEVERAL weeks and you need an ammonia source such as a FEW fish or doing a fishless cycle see the article on this site
i tried doing it with fish and it was a mess they kept getting sick because of the stress i was putting them through so now i'm doing a fishless cycle
from what you say it seems you set up the tank let it run for a week and then added 30 fish. if this is what happened i dont think you will be able to keep the ammonia down with out doing water changes like crazy, the ammonia will spike and the fish that dont die from that might die from you doing water changes, it's stressful for them and when fish get stressed they get sick and die
so most likely all your fish will die
also your painted glassfish are a dyed fish, aside from being very cruel it also makes them less healthy and if they do survive the will eventually lose their color when there immune system rids it's body of the poisons that have been injected into its body