I am a noob in fish keeping and bought a 10 gallon aquarium 2 days back. It had 3 neon tetras, 5 guppies and 2 Indian glass fish.

On the first day one of my guppies started coming to he surface quite often and it had trouble swimming. By the end of the day it got stuck in the plants and started breathing heavily and died the next day. All my other fish also died in the same way. Now, I have only two neon tetra and don't want them to die as well.