It's on the 200v setting and ranges from 1.2 to 80-90v at different times. I think I'm Reading it right. Just the idea that it's affected by the lights is odd. Isn't it? The gfci power strip is on the right of tank. The power strip for the lights is on the left. Nothing on that strip touchs water. How could it affect it
Sounds like you are reading it correctly.
Inner Geek Alert:
When the first electric grids were being formed to rather famous individuals, Tesla and Edison, were competing to get their preferred method of generation to be adopted. Edison wanted DC because the voltage was easier to regulate, it was safer, and the technology was more mature. Edison rather disturbingly electrocuted an elephant using AC current to try and make his case. Tesla won the battle of the currents anyway, and the AC distribution system was born. Why did he win? Transformers. The Autobots and Deceptacons came.. uh wait.. wrong story. The largest single power loss in a distribution system is due to heat generation from current. The heat produced is equal to the square of the current times the resistance (P =I*I*R). Another power equation is P=1.732*V*I*pf. if you raise voltage, you can lower current and greatly reduce your losses. With DC generation we would have needed a power plant every few city blocks. Thanks to transformers we can raise voltage to very high levels and distribute power over long distances with minimal losses.
In its most simple form a transformer is nothing more than a steal core with 2 separate coils wrapped around it. The proximity of the two coils allows the magnetic flux from one winding to generate voltage, through induction, in the other winding. By controlling the number of turns in each coil we can control the output voltage of the second winding.
Ok, back to the subject at hand. Why does the light matter when it isn't touching the water? A transformer is proof that if you have an AC current source near a conductor, it will generate a voltage. Salt water is a conductor. If the power cord of any electrical component runs outside and along the tank walls it will induce a voltage into the water. If you have a power cord that runs next to part of a power cord that runs next to the aquarium you can induce a voltage in the aquarium. As long as you have a magnetic field within the water of the aquarium, and relative motion between the magnet and the water, you will induce a voltage.
One of my biggest concerns is that you may be seeing these big fluctuations not because of the induced voltage, but because of a problem with your ground. If your ground prong isn't properly bonded to both earth, and the transformer neutral the feeds your house, you can get some very odd readings. A good way to test the ground within your house is to run a 3 prong extension cord from an outlet on a different circuit to where your tank is. Then use your meter set for resistance to check the number of ohms between your power strip ground and the ground on the extension cord. You should get less than 1 ohm.
