This article could help you decide. Discusses special needs & maintenance of seahorse tank:
Keeping Seahorses in Aquaria #1 - Introduction and Setting Up Your Seahorse Tank
This article is the first in a 6-part series that is designed to help those of you who already have the knowledge and ability to keep marine life...
By vlangel, Apr 18, 2017 | 2.9K Views | Saltwater Fish
Thanks for the link. I currently have the 70 setup as a seahorse-pipefish tank. And I love them. That's why I was thinking about giving them the 125 then the 70 would be my hawk fish/other fish. Just torn with which should be which