Used to keep marines some years ago. Some tips when buying marine fish:
- Active n swimming doesnt mean healthy. Cyanide damages the internal organs.
- Only buy fish tat u see eating with gusto.
- Can try food supplements like garlic extract, or SeaChem Entice.

Bi-colors r finicky eaters. Some will eat pellets, while others die-die also wont even smell it. Took a long time for me to find one tat eagerly took to pellets. Take ur time n wait&search for one tat eats pellets.

Happy marine-ing