my problem is that when i turn on more than 10-20 leds at the same time the leds are not bright enough.
Im powering the led cube form arduino uno.
Well, that's why.
Each resistor is 5ohms.
That's generally way too low.
If i have used 25 resistors one for each anode would the leds be brighter?
More resistors/more resistance == less current. Less current == dimmer.