Why you think machines cannot do this?
Machines are used even today for re (no: for new)forestation. In fucking China, not some high wage area!
Fish habitats... not fully automated, but hydroponics already has fairly automated processes, and tehr eare even plants involved, not only fish.
Yes we can automate these things to some point but with 80% of world fish stocks gone we are not doing a very good job ..
There are tons of unprofitable thi gs that need doing and need doing badly that are not ... It would solve the work problem and clean up the planet as it is a bit of a mess.