Photocell add-ons

The LED array is off on the near side, where photocells are, but the breadboard LED isn't ON like it's 'sposed to be with no light input. Why?

I have to hold the already heat-shrunk tubing even tighter to block light, these photocells are persnickety

       In lieu of taking out LEDs and directly tapping the current flowing to them, I am tacking some photocells into the circuit and using that analog input to drive the OTHER, RGB LEDS. Yes, this is ridiculous. At first I took an LED out, soldered wires, and tried to get a serial print of ANY readings off of it.. but failed. My professor urged me to leave em in and heat shrink tube-wrap some photocells on top. So I dragged my feet for a few minutes and then I did it.

       Reading into pull-up/pull-down resistors. The photocell alone is giving me some funky readings and there are, as usual, several possibilities to consider: 1) my code. Coding is not my forte, and this is a likely candidate. 2) the tubing isn't blocking light well enough, especially from the nearby LEDs.  3) I need a pull-down resistor? I guess that analog sensors have a tendency to float, or are "high impedance," and I could cut weird readings this way.