Hello everyone. This is my first time in this forum. I need some advise on keeping goldfish. In the last few months I had 3 small goldfish in a XL sized bowl without any filteration or oxygen. The water was changes every 3 days. But they got well.

Recently I bought a 2 feet aquarium. basically I used filtered water as usual add in some anti clorin and used the same pebbles. This time I added small filter and air bubble system. When I transfered the Godlfish they all die on the next day.

I cleaned the whole tank and bought some gold fish again
The next day they also died by next morning.

Then I bought 2 big goldfish, each cost RM5 again by morning they were floating upwards and pass away the same day

Then i cleaned the tank pour more anti clorin (half a bottle) and put 3 more fish, 2 gold fish and 1 angle fish. The 2 gold fish died again. The angel fish died after 4 days.

I now dono what to do... why is the gold fish dying. The tank is now 10 days old and I have bought 2 udang instead now.

Can someone help me.. goldfish is so nice to keep, how come in the little bowl they survived but in a bigger space with filter and air bubble they dont>

Thanks