That code just causes the LED to start at maximum brightness and reduce down at a rate set by the potentiometer, then it starts over (i presume i can add the other part of the code in easily enough to make it ramp back up again).
Yes, you can.
However, if i reduce the potentiometer down to minimum and then up again the LED halts it's cycle and does not restart. Exactly the same problem as with my code.
Aha, now we get to the real problem!
Look at what the fade amount is when you get the potentiometer to the lowest value.
int sensorValueRed = analogRead(sensorPinRed);
int fadeAmount = sensorValueRed/300;
When sensorValueRed is 0, fadeAmount is also 0.
If you start with b=255, and sutractt 0 on each pass, how many executions of the loop will be required to get b down to 0?
Clearly, you need to constrain fadeAmount to not less than 1.