I won't comment on the original question regarding adding too much food accidentally since that has already been addressed.
Definitely test your aquarium daily for ammonia and nitrite since this is a newly set up tank and your beneficial bacteria is probably not robust enough to process the bio-load of the 20 or so fish that you have just stocked in this tank. Keep a written record of the water parameters for ammonia, nitrite, nitrate and pH and be prepared to do frequent, possibly daily water changes to keep the ammonia and nitrite as close to zero as you possibly can as those are most harmful to your fish.
It would also be helpful for you to write down the names of the fish you have so you can keep track of them in the future. I know you asked for help in identifying at least some of them and Neutrino posted about 2 species that will get too large for this tank so you may want to consider returning them to your fish store now to avoid problems down the road.
Definitely test your aquarium daily for ammonia and nitrite since this is a newly set up tank and your beneficial bacteria is probably not robust enough to process the bio-load of the 20 or so fish that you have just stocked in this tank. Keep a written record of the water parameters for ammonia, nitrite, nitrate and pH and be prepared to do frequent, possibly daily water changes to keep the ammonia and nitrite as close to zero as you possibly can as those are most harmful to your fish.
It would also be helpful for you to write down the names of the fish you have so you can keep track of them in the future. I know you asked for help in identifying at least some of them and Neutrino posted about 2 species that will get too large for this tank so you may want to consider returning them to your fish store now to avoid problems down the road.