Fish load question

I have a 55 gallon tank with a vermiculite/soil mix covered with gravel.
Lighting is provided by 4 40w daylight tubes that are on for 13 hrs 20min a
day. CO2 injection is by a canister with an airline tube to a powerhead that
sprays it out into the tank. Filtration is by a Magnum 220 with gravel in the
chamber. I add PMDD everyday, with roughly 33% water changes every week. The
plants are a large Amazon sword, dwarf and pygmy swords, red ludwigia, rotala
macandra, water sprite, ambulia, bacopa, red crypt wendtii, hornwort, and
corkscrew vallisneria. The fish popualtion is 7 neon tetras, 6 otos, 2 black
neons, 2 white cloud mountain fish, 2 red eye tetras, 2 lemon tetras, 1
betta, 1 clown loach, 1 pleco, and 1 flying fox. I feed them once a day with
Tetra Ruby and, infrequently,  freeze-dried bloodworms and algae wafers. My
question is, for this kind of setup would this be considered a moderate or
heavy fish load (I assume it wouldn't be considered light), and if it is
heavy, how heavy? Would it not be advisable to add any more similarly sized
fish (hatchetfish, danios, barbs, rasboras or other tetras for example)? How
about any larger fish types (gouaramis, angelfish, etc.)?
One quick unrelated question, will neon and cardinal tetras school together?

                                                Thanks for any help,