Neon tetras in groups of at preferably at least 6-8, corydoras in groups aswell (threesome is not a group, really).
In nature cories live in loose groupd of hundreds of the same species, and neontetras in groups of thousands of the same species, so 1-3 is really very little. ****
BUT your tank will not fit them all, so maybe rather leave them in a store than make them live unnaturally in too small groups in too small space, right?
And the frog waste will quickly spoil the water. It is toxic to fish and in that small space it happens quickly. ****