slime...

So today when I was taking the ph and ppm levels of my solution I notice a slime on the surface of the water in the reservoir. It literally looks like someone spit a bunch of mucus into my resevoir. any ideas on what this could be?

can/does light get to the res water?

sounds like you have low oxygen levels in your reservoir. 1 watt of air pump per gallon of water, and depending on your system you should consider a pump in the reservoir in order to "stir things up."