60L ~ 15 US gallons. the rule of thumb is about 1 inch of fish per US gallon.
1 betta is about 3 inches of fish. that leaves you about 12 inches to play with--enough for a big happy group of
cory cats!
some species like the bronze/albino cories get to be about 3 inches.
other species like the bandit, jhulli, and spotted cories get to be about 2 inches.
the false cories (brochis species) like the emerald cory get to be about 4 inches.
the long and the short is get about 5 or 6. you can fudge on the inches with cory cats, so long as you don't overfeed and keep up with cleanings. you do need rather small, light-weight, rounded gravel. otherwise the pebbles will damage the cory's barbels as it searches for food. damaged barbels are a leading cause of death by bacterial infections and starvation in cory cats.
-----------alternatively------------
there are a variety of smaller loaches available. i suggest asking around in Cynaprids & Characins, but off the top of my head... chain loaches, khulli loaches, skunk loaches, and bengal loaches are all sized appropriately for your aquarium. but i can't speak for temperments beyond the khullis (which are about as angry as cory cats, which is to say, not at all
)
the loaches are a bit bigger and messier than cories, so a group of 3-4 would be good.
you don't really have room for both, however. both are very sociable types of fish and do much better in larger groups. best of luck! (oh, and i
love your name
)
