Did this wall adaptor power the leds in the tank (fish tank?) originally? Is it regulated?
The wall adaptor did power the leds originally. I pulled the wires off the switch that alternated between Off, bank 1 and bank 2 and ran them into the MOSFETs and ground. Its a simple wall wart that puts out 12VAC - it runs into the filter first and then into the lights. I checked for AC running into the leds and didn't see any indications on my meter, so there I'm guessing there's a rectifier in the base of the filter.
Well those FETs are wrong for a start. They need 10V on the gate to fully turn them on and you only get 5V from the arduino.
However your description would suggest there is something else wrong as well. Perhaps it is not wired the same as the schematic. If it were the problem you should get is that the LEDs are not coming on fully.
That's what I figured, but they get fairly bright when the PWM is fully on. I went over everything last night thinking I had hooked it up wrong, but maybe I missed something. I'm starting to think its time to pull everything off the perfboard and put it back onto the breadboard for testing.
I think I'm more looking to make sure I don't need diodes somewhere before I etch a PCB. I will be getting logic level MOSFETs for the next iteration - I figured the VGS(TH) 2V (min) and 4V(max) that I read on the datasheet would be sufficient. I keep thinking there's current leakage somewhere, but can't figure out what would be causing it.