Testualm eggs lay partially buried underneath vegetation at the edges of sandy beaches. If you want a Testualm to hatch properly it is best to leave them where they are, moving a Testualm egg can result in death.
Testualm have a symbiotic relationship with various beach plants, mainly palm trees. Due to this relationship Testualm tend to swim at or vary near the surface of the ocean, diving deeper for only short amounts of time.
Testualms never really stop growing. There have been some reports, and many a sailor's tale, of small floating islands that disappear or move and are attributed to Testualms of extraordinary size and age.