I am a true believer in life from space rock. We have no way of know exactly how life got here but still. Earth was sterile at one pion, so was the fishtank (not including bacteria). Earth is an enclosed system and so is a fishtank. I had a comparison: Have you ever done that middle school project in bio where u put 2 soda cans together with the one on the top having some grass and crickets in it and the one on the bottom has a water plant a guppy and a snail? If so the u created ( or attempted to) an ecosystem. That is what i meant.
I think you need a refresher on what an ecosystem is...