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.
Blue crayfish are omnivores, and they are great scavengers. They will eat plant detritus from the tank, in addition to most other foods. You can supplement their scavenging with fresh vegetables and any kind of fish or shrimp food, such as flakes, pellets, and dried algae.