That's looking at it as a zero-sum thing. You're not choosing between an algae tank and a utopian solarpunk city with no cars, tree lined streets, and bikes and grassy trams every where. You're choosing between an algae tank and all its benefits, or no algae tank. I would choose the algae tank over nothing any day. Would I take it in place of a perfect solarpunk city where we all live in trees and get around with rope bridges? hell no.