Addressing
Cheilodipterus quinquelineatus first here.
These are more social than a lot of other cardinals in the wild - they're typically found in fairly large aggregations during the day, reportedly in numbers of 5-30; at night, they're sometimes alone but sometimes in groups of reportedly 2-5. Keeping 5+ is recommended.
They prefer living either in Acropora branches or the spines of the Longspine Sea Urchin,
Diadema setosum.
Like other cardinalfish, they're nocturnal, and night is when they do most of their feeding. They're known to feed primarily on small crustaceans (pods, shrimp, etc.), small fish, and occasionally snails. In aquariums, they're also reported to occasionally eat worms, including feather dusters.
They are mouthbrooders, and have been aquacultured before with reportedly high survival rates.
For the Ostorhinchus species (which are also mouthbrooders),
O. cyanosoma and
O. compressus have both been aquacultured before as well with similarly high reported survival rates.
Both are also nocturnal. Keeping a group of 5+ has been recommended for both of these as well.
O. compressus is reportedly found among branching Porites species such as
P. cylindrica and
P. nigrescens in small groups.
Not as much reported info is available about the wild diet of
O. compressus, but it's assumed to be similar to that of
O. cyanosoma, primarily feeding on zooplankton (pods) and benthic inverts like shrimp. It's considered invert safe with caution.
O. cyanosoma is reportedly found typically under overhangs/in caves, but they are also known to be found in the spines of longspine sea urchins. They reportedly are typically found alone at night, but sometimes they're found in pairs. It is found in small to large groups during the day.
They reportedly feed primarily on zooplankton (pods) and small, benthic crustaceans (such as benthic pods and/or shrimp). They also reportedly may feed on small worms, including feather dusters in our tanks.
