Ranitidine is a competitive, reversible inhibitor of the action of histamine at the histamine H2-receptors, including receptors on the gastric cells. Ranitidine does not lower serum Ca++ in hypercalcemic states. Ranitidine is not an anticholinergic agent.
1 The Blue Marlins have a diet of: Octopi, squid and pelagic fish such as black fin tuna and frigate mackerel.  They do prefer to hunt alone and during the day, rather than in schools, so it is safe to say they are a rather antisocial species.
If you are storing live blue crabs in the water, you will need to feed them. Adult blue crabs will eat oysters, hard clams, dead or live fish, crabs (including blue crabs), shrimp, organic debris, aquatic plants, and the leaves and shoots of sea lettuce, eelgrass, salt marsh grass, and ditch grass.