I recently stocked my 20 gal tank with 6 White Cloud Minnows, 4 Zebra Danios, 4 Golden Otto, 4 Rasboras, and 2 Corydoras. All of my fish except the 2 Corydoras, tend to stay close to the surface. Is this natural? Thanks
Yes this is usually either an oxygen related issue or a issue with the water quality. In any case, unless you fishless cycled this tank properly, chances are you over loaded this tank too fast.
IMO it's not overstocked at all, provided its been cycled. The minnows are...well, minnows! The danios are small, as are the ottos. The cories dont really take up much space, and none of the fish mentioned create lots of waste. Things seem fine as far as stocking goes, but we do need to know if it's cycled yet.