Hi,
what filter do you have?
i think even if its standard juwel filtration that level should be no problem with regular water changes and general tank maintanence.
Id maybe add one new species at a time so as not to overload the filter.
Another consideration is that when the angels get bigger, neons may be on the lunch menu, so perhaps swap them for something like a shoal of the slightly larger cardinal tetra or maybe emperor tetras or rosy tetras.
Red tailed black sharks are notoriously territorial so maybe leave him out.
6 corydorus is a good idea, they like being in groups and add great character too.
Happy fish stocking.
Cheerio,
Ady.