Seems like a real stretch to compare a 5 gallon tank with one fish and one plant to an entire planet with diverse plant and animal life, biomes, geography, etc.

Seems like a real stretch to compare a 5 gallon tank with one fish and one plant to an entire planet with diverse plant and animal life, biomes, geography, etc. Sure, there’s a finite number of species that exist, but scientists discover new species fairly regularly. You never know if you’ll walk over the next hill and discover a new bird species. Try doing that in a small tank with one other multicellular organism.