Nah, he still wants it. It'd just take too long to climb all the way down and get it.

As Richie deposits the fish back into the tank, Grogu climbs back up. He reaches one hand into the water and a different fish seems to swim backwards for a moment as it's pulled into his hand. Grogu thinks the guy is too distracted by the other fish to notice before he stuffs it into his mouth... But who knows.