UPDATE:
So yesterday morning I went down to do some water testing on the tank and when I put my fingers in the tank to draw some water I swore I felt a tingle up my fingers. Yikes! :eek2: So I did some deductive analysis and thought I had a couple of bad heaters. I called Hydor, the company that makes the 2x 200 watt Theo heaters I'm using to see what was up. Mike at Hydor instructed me to pick up an analog voltmeter to make sure there wasn't any stray voltage leaking into the tank from one of the devices.
After testing I'm not exactly sure what to think other than my hands are a little chapped from the weather change this last week so I could have just been feeling the salt on my fingers. The voltmeter testing shows 0 stray voltage... Hmmm.

But in any event I'll continue to monitor it now that I have the proper equipment.
The voltmeter that was recommended to me was an AC analog voltmeter, or multimeter. This is opposed to a digital voltmeter that in some cases show nominal noise during testing that can give false readings. Mike explained since saltwater is so conductive the digital meters can essentially get 'confused' as to what's actually "real" voltage. Makes sense, I guess... :lol:
Here's the voltmeter I picked up from Home Depot. Sperry SP-5A, costs $7.
Closeup of the voltmeter. It measures AC, DCV, DC mA, and OHMs.
I also picked up an outlet tester to rule out any possible grounding issues or reverse polarity issue with the conduit run I installed. This meter simply plugs into a receptacle and lights up according to the either correct or incorrect wiring it reads. I'm proud to say all my receptacles were correct. Haha
GB brand Outlet Tester model GRT-3500, cost $3.