Harden; Literally, Turn to Bone
This page is the CodyCross answer for the clue below from All Things Water, Group 1281, Puzzle 2 (Tropical Fish).
Question is: Harden; Literally, Turn to Bone
and the answer is: OSSIFY
Word Meaning:
OSSIFY — (ambitransitive) To transform (or cause to transform) from a softer animal substance into bone; particularly the processes of growth in humans and animals.
Definitions from Wiktionary.