Perhaps the single greatest issue, and the least offered solution in troubleshooting the home aquarium has to do with electricity. In many cases, poor fish and invertebrate health or even death, has as much to do with electricity "leaking" from various devices as the usual suggested checks of the Nitrogen cycle (ammonia, nitrite, nitrate), pH, salinity and alkalinity. I mean, c'mmon... We're sticking an electrically powered device into water. Your mother would have fits! :) The good news in all of this is that it's simple and inexpensive to identify and correct.

A little about electricity

There are some certain basics everyone should understand about that receptacle you've plugged a thousand things into during your life. I'm going to be very basic for our purposes, so please don't scorn me with "Well, sorta but not exactly" :)

The first item to understand are the "holes" and the "prongs".

The smaller straight hole is the "Hot" lead. This is where the electrical service comes from your breaker box. It doesn't "do anything" so to speak, that is, until it makes a connection to something (whether that's metal or, your finger ;). It has a very high potential.

The larger straight hole is known as the "Neutral". This is where and how current is created, and powers electrical devices. When a device is plugged in, it takes the potential from the Hot lead and completes a loop back to the breaker box via the Neutral. A practical example to understand this is a switch on a lamp. When "turned off", the switch interrupts this loop and leaves the Hot at its former "ready" state.

You've probably seen wall receptacles with just these two holes. Certainly you've seen electric devices (look at your tank equipment now ;) with two prongs of corresponding size to the holes on their plugs. What is that third round one?

This is the ground. It's not necessary, so to speak, because any electrical device will run without it. However, it's an excellent safety precaution (much like a seat belt in a car) to avoid electrifying devices switched off that have somehow failed to keep the Hot in it's "ready" state. It takes this stray potential to somewhere (hopefully an earth grounded rod outside of the home) and you avoid getting "bit" by the device. Additionally, since electricity goes the path of least resistance, it's better suited than say, your body, to accept the voltage. A senseless shocking has been thwarted.

Additionally, the screw in the face place on the receptacle should be connected to the ground wire as well. I will give this some extra discussion a little later. Let's look at how to test all of this...

Using a Multi-tester

A multi-tester is a device that electricians use to test wires and wiring. It's a common tool to have, so you may already have one. They range widely in price and functionality. A simple multi-tester runs on any voltage it finds, which causes a needle on the unit to move accordingly. Basically, if the dial moves when set to the A/C setting, you have voltage. These multi-testers can be purchased just about anywhere with a hardware section for $10, and are all you would need for finding stray voltage in your aquarium. Digital multi-testers are also available, yet they are more expensive based on what functions they have. I've done a fair amount of electrical work, so I spent the extra money for the digital.
Another tool to have is a receptacle tester. They cost $5 and are good to have around the house regardless. They'll tell you the status of a receptacle, whether it's wired correctly or not. This is also good to test the receptacle you'll be plugging the grounding probe into. If the receptacle isn't grounded, there's no point in using a grounding probe ;). We could discuss other uses for the multi-tester in doing electrical work or testing a receptacle, but let's get to our purposes here. How do I use this device to test my aquarium? It's quite simple: 1) Set the dial on the face to the *lowest* A/C setting (usually 5) for the simple testers, to A/C for the digital. 2) Stick one probe in the water, the other to something metal, preferable to the screw in the faceplate of a known grounded receptacle. If you're going to use the screw, assure that there isn't any paint on it. 3) If the needle moves, or your digital display reads any voltage, it's time to ground that aquarium. That's the hard part ;) Now what to do about it, if we've found anything... Now that I've found it, what do I do?
My suggestion if you find *any* stray voltage is to get a Grounding Probe as soon as possible. They cost anywhere between $15 and $20 and come with a titanium probe that will not corrode in the saltwater. Many local fish stores carry them and most mail order places have them as well. You place the probe into the water somewhere and then just plug it in. Very simple. Test again with the multi-tester. You shouldn't be able to read anything. On a good digital multi-tester, you'll probably read something less that 1.00.
A *temporary* solution is necessary for the interim as you may have some animals hanging in the balance. I've found that a piece of stainless steel like a bike spoke (or you can use a titanium bike spoke permanently) or an old spoon paired with some speaker wire will do just fine for a week or two. A piece of clothes hanger will work as well, provided it's not copper, however, they tend to corrode more quickly. Bend the metal to hang over the edge of the aquarium, strip the plastic off the end of the speaker wire, wrap and make your connection on the end that is *outside* of the water (do not get the speaker wire in the tank, it's copper). Unscrew the nut on a known grounded receptacle, wrap accordingly and screw back in. Test it with the multitester. I highly recommend that you plug your grounding probe *into* the receptacle or a properly installed six way splitting plate. I recently discovered that a receptacle in a power strip had become ungrounded, and of course, that was the one I had the probe plugged into. Additionally, the six way splitter I moved it to wasn't installed properly, and the long and short is… It was another 24 hours before it was properly grounded. One melted large colony of xenia, two bleached Stylophora, one recessed Acropora and a sick fish later.... Yeah. Please don't make this mistake as well. Remove the faceplate on the wall receptacle and screw in the six-way plate. Test with the receptacle tester to assure a solid ground. Electricity is nothing to be lazy about. Symptoms in the Aquarium Here are a few of the symptoms (outside of death) I've observed or been explained in various shockings: Fish: Continual scratching Lateral line corrosion Strange fungal infections along the lateral line or on the mouth/forehead Coral: Extensive loss of zooxanthellae in SPS and LPS coral Tissue recession and polyp bail-out in SPS coral Shriveled up and discolored soft coral Complete "melt down" of soft coral Leather coral shed excessively and will not extend their polyps Tridacnid Clams: Retraction of the mantle, sometimes in only one place Central bleaching of the mantle Shrimp: Excessive molting I've also observed gray or green phytoplankton blooms (cloudy water). Strangely enough, this all immediately *ceases* once the tank is at ground. It's almost like you've removed an evil presence from the system (well, you did ;). Within 5 minutes the tank looks relaxed, the fish are ready to eat, the coral start doing what they need to next. A little prevention goes a long way I'm not sure why a grounding probe isn't the first thing offered to new aquarists by shops when buying their system given their cost and benefit. I'll avoid conjecture as to the seller's reasons, and just point out that one dead fish or coral is probably twice the price of the probe, let alone the needless waste of that life which I don't think *any* aquarist wants to see. If you've not been informed, it's not your fault. I'm glad you're still with me here :) In all instances of my aquaria (marine and freshwater) I start out with a grounding probe. I've seen every type of device in every type of aquarium system leak voltage. Powerheads, heaters, whisper filters, etc etc. My VHO setup on my 125 even chips in 10 volts! I discovered that when I lost the ground on the powerstrip the probe was plugged into. I'd heard of what I've read described as "resonance" happening, but was totally "shocked" when I actually saw it. As well, I've read a lot of Bulletin Board and Email posts about certain devices "Nuking" a tank. I've often asked those individuals if the tank was grounded. I've never even gotten the pleasure of a reply and must assume they didn't. Really, if my assumption is incorrect, I'd like to be corrected (I'm not trying to rub it in at all, I just want to know :). However for now, I will venture to guess the trauma could have all been avoided by having a $15 device in the tank and plugged into the wall. So to summarize, there's absolutely no reason to have your animals experience any of this. This is definitely something to consider when setting up, and certainly something to check if you're seeing some problems.