You can try most frozen foods. Blood worms is a favorite in my tank, but you don't want to feed them too often because they are very fatty and can lead to a fish becoming constipated which can lead to swim bladder problems. There are many other foods out there. Its hard to tell you how much to feed because I don't know how many fish you have.
Other favorites include peas (deshelled), cucumber, zucinni, the clown loaches love bananas but those need to be taken out very quickly like within 30 min, to not mess up your water. I have heard of people shredding and cooking carrots. I have done lettuce and spinach before.
On a random note, my fish love algae wafers and sinking shrimp pellets. I don't have any tetras, but i am talking about a pack of tiger barbs swarming around an algae wafer or my opaline gourami, duddly, marking his territory off when shrimp pellets are in the tank and literally chasing everyone else away.