My family bought a fish tank randomly.
We applied the rocks, deco and water as well as the conditioner stuff. When my dad bought them they said to wait at least 5 days. But my mum and I researched online and people said they didn't Have to wait. So 2 days later we bought 4 adult goldfish and one baby goldfish.
After one week all the adults died, but the night/day before they died they would lay under the decorations or on the rocks. But the little one is still alive.
So why did they die?Did we need to wait a week? Or is it because the adults were over feeding? Any ideas.

My fish tank is around the size of this fish tank at this link.
http://www.aqueonproducts.com/products/bow-front-aquarium-kit.htm