Auto Fish Feeder

I would like help making the fish feeder, i was wondering if i could use a endless screw(or archimedes screw) and some stepper motors, to carry the foo for a certain time and dump it in a fish tank with aprox 25-35 fish

Yes

how to you test to know
#1) that there is food being dumped ?
#2) the quantity being dumped ?

I do not know the volume you need, but you could fill a tipping bucket. use a sensor to know when it is full.
use the screw to fill the bucket,
once full, dump into the tank.