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Electricity Use and Aquariums


By Bob Fenner



Remember back to a time when you were part of a black-out or just a brown-out experience, or visited a foreign country where your electrical plugs didn't match their bizarre looking outlets? When the "juice" is out or unavailable, it's no joke--especially when you suddenly try running your tanks without air, light, pumps, filters or heat.

Like all modern marvels, electrical power only seems to be appreciated when it's no longer available. Consider how easy it is to access, so powerful and clean; a ready slave to drive motors, make heat, light, move water, air, ourselves. Because we are so accustomed to electro-motive force being at our whim and will, there is a danger of complacency. Electricity can be a real hazard where our hobby is concerned. Lighting, heating, pumps, meters, ozonizers, ultraviolet sterilizers and their wiring and plug connections are potential sources of electrical leaking, shorts and shocks. As the old sayings go: "Water and electricity do not mix"--or-- "Water and electricity mix all too well."

Water can get around insulators through condensation and failures in insulators themselves (wiring, plugs, fixtures). You may personally register the degree of leaking as something from "tingling" to an alarming shock. The negative effects on livestock of small stray voltages around aquaria are an area of large controversy. There are devices sold 'off the shelf' that purport to measure or effectively 'drain' off errant electrons. The furthest I'll go (so far) is to say that stray electricity is very likely not good for you or your aquatic life.

Actual shorts are the result of a loss of insulation. A short circuit fully energizes another unintended part. The full potential current is now available to have your body complete the circuit to ground; this occurrence is known as severe shock or electrocution.

How many ways can this happen? Chaffed wiring, grabbing after a light fixture fallen into a tank, a cracked light socket, split U-V sterilizer lamp, broken glass on a heater, saltwater dripping onto or creating a bridge into an extension or multiple outlet device--serious accidents caused by these problems happen several times a year.

Avoiding Electrical Hazards:

1) Examining cords, plugs and outlets is obviously something aquarists should do every time they work on their systems. Wearing insulating shoes and standing on a dry floor when you have your hands in the water is a very good idea.

2) Creating drip loops in wiring and flexible tubing that services the system goes a long way in keeping saltwater out of appliances and outlets. Just coil and tie off (with plastic pull-ties or even sandwich bag fasteners) a loop or more from each cord and length of tubing; water will follow the line to your loop and make a neat stalactite at the bottom of the coil instead of where you don't want: in plugs, electrical cord insertions and pumps. This low-technology is simple, and it works.

3) Mount multiple electrical outlet "power bars" and extension cords up off the floor, either on a vertical surface or upside down away from places saltwater can fall or splash into them. I was self-employed for 18 years doing ornamental aquatic work. Our Service Division designed, built, installed and maintained live-holding systems; mainly large marine aquariums in commercial and wealthy residential settings. We discovered not only that aquarium wiring can cause fires, but that such conflagrations were common enough in California that we developed a side forensic business investigating and testifying regarding aquarium electrical failures.

4) Pull the plug on heaters every time you're going to do anything with water levels. Many more heaters are sold than aquaria (I've dusted dozens) from careless emersion or submersion; the glass housing can shatter in an instant if removed from the water while hot or plugged in while dry and then plunged into the tank.

5) Be aware that Styrofoam and acrylic have low flash points and are relatively flammable. Store Styrofoam boxes away from potentially over-heating electrical wiring, pumps, et al. and acrylic. Be especially wary of older, tar-type ballasts (wattage transformers) used with most fluorescent lighting and ultraviolet sterilizers. They get too hot (anything uncomfortable to touch) to store in closed spaces or on acrylic surfaces.

6) If you can, avoid using extension cords altogether, and never plug one into another. If you are installing heavy-duty pumps, chillers or lighting, consult an electrician or learn what the A.W.G. symbols for wire gauge really mean in terms of rating, load and run (length). 7) To check for suspected gross electrical leaks, buy a cheap but useful test lamp device; it makes a good addition to any aquarist's tool box.

8) Install and maintain gear per the manufacturers' specifications.

9) Please use a ground fault interrupter (GFI--see accompanying article) with the kill-a-watt spider webs of electrical cords that will develop behind your aquarium.

This technology is so readily available, easy-to-use, and cheap that even I believe it should be industry, (maybe, choke) governmentally mandated. If you embrace nothing else by allowing me to share my thoughts with you, get and use G.F.I.s. About 95 percent of all home electrical injuries, including about a thousand electrocutions a year in the U.S., are caused by Ground Faults. Avoidable by, yes, you got it, G.F.I. protected circuits. Think your sub-panel is going to save you? The amount of electron loss to pop a breaker or fuse is much greater than that necessary to overheat, destroy insulation, to zap you, and start fires.

Electrical Efficiency: 

One of my favorite words because it has "fish" in it; efficiency is an important consideration in this world of high and getting higher electrical costs. Be aware that there is a huge variance in electrical consumption versus relative light produced, air and water moved. Here's a formula to remember:

Volts times Amps equals Watts

You pay by the kilo-watt-hour, the equivalent of 1,000 watts used for a period of one hour's time.

Volts X Amps = Watts

Watts/1,000 X Hours On X Electrical rate = Cost / day


If you are confused or have concerns about the adequacy of your aquatic electrical wiring? Good; call your local utility. Most of them have folks that will come out for free and check out your arrangement, explain how to tell what's costing how much, and to give suggestions on how to reduce costs and prevent loss of life and property.

Temperature Control 

Name the substance in all of the universe that can 'take up' or release the most thermal energy. What is it? Water; again the big winner as a standard; this time for specific heat, the scientific measure of caloric content. This trait points up the reason for overall steadiness in the world's largest heat sink, the oceans. [DUH....I thought that certain Zeolites were actually more efficient at storing heat???? Seems to me that solar-energy types were trying to use Zeolites in the 1980s as compact (more compact than huge tanks of water) energy sinks. Gosh, Mr. Wizard, who's right?)

Most marine systems/organisms do best between 70-80 degrees Fahrenheit, optimally around 75.F for most. What is key to successful marine aquarium keeping in terms of temperature is stability. Ocean life enjoys an environment that not only varies little thermally, but further, is one that many organisms can move to or from if thermal gradients arise. Such is not the case with our tiny captive volumes. Attached or sedentary organisms are especially vulnerable to large and quick changes in temperature.

In captivity brief forays slightly above 84 or below 68 are generally not disastrous if they occur gradually and all else is well, but they are to be avoided. This is the realm of temperature control.


The expense to heat and/or cool marine systems are frequently the hobbyist's largest expense (Frank, 1983). Does this surprise you? Specialty lighting and fluid-moving pump costs are often large as well; and the waste heat they add to a system also figures into the temperature control equation. A conscientious marine aquarist will take care to do all he or she can to reduce temperature fluctuation and cost of thermal maintenance. Though not often discussed, system construction, size, shape, placement and insulation are key elements.

Preventative Heat Loss/Gain Measures: Determining how much heating you'll require is to some degree a matter of empirical study; correct--guesstimation. You want to have to have as little as possible for costs and other reasons.

Tank (and possibly sump) construction, size/shape is very important. Notably acrylic is far superior (about five times) in thermal insulation property (for these and other materials see Sams and Webb (1979)). With size, the bigger the better; larger volumes contain more heat energy, hence are more stable. Additionally, big tanks have thicker-walled, better-insulating panels. Shape, for once favors my body plan; the more cuboidal tanks have less surface area/heat loss. [BOB: We just told them more surface area is better. Can't have it both ways. I'd cut this--how many people are going to buy a tall and narrow tank so save energy?]

Placement: Add to your reasons for not placing your tanks close against outside walls, besides mildew and not being able to work around them, the fact that those walls are energy magnets. I've seen tanks heated and cooled unbelievably by walls, as well as the more obvious doors, windows and heat ducts.

Insulation: This becomes especially important in cool or cold water systems where you have to fight the gradient continuously. Some lucky wholesale manufacturer will read this, and start supplying bottom, back, and possibly top and side insulation panels. Sumps too should be heat/cold shielded.

Heat loss by evaporation: This, too, can be extraordinary. The most heat leaving your system may well be from the partly or totally uncovered aquarium and/or sump surface. If you're losing water, you're losing thermal energy.

Lighting & Pumps: 

These and other pieces of equipment all can be guilty of adding too much heat to a system. Consider turning on your super-nova lighting in the evenings when ambient temperatures are cooler; when you schedule day and night for your aquarium does not matter to your livestock.


Though there are quartz, hot air injection, in/under tank pad types and many, many more, most hobbyists will use glass-walled electrical resistant heaters. These popular modern devices are comprised of a printed circuit board, heating wire, thermostat and indicator light housed in a heat-resistant glass tube.

Never, ever take a chance with cheap heaters. Bargain-priced, thin-walled, reception-interfering, thermostat-sticking units have wiped out thousands of tanks, zapped millions of fishes, even killed hobbyists; and they're still on the market. There are some reputable external heater manufacturers, but I'll make it easy on you, and hopefully avoid defamation lawsuits: just stick to submersible heaters. These are inherently better because of their sealed components and ability to be placed low(er) in the system; warm water, like air, rises.

Wattage: How much is enough? For the vast majority of systems somewhere between three to five watts per gallon. Smaller tanks with no top, in cold buildings need more; big honking ones with thick walls and large thermal masses, less.

To be safe, it's always better to buy two smaller heaters than one large unit. For example, say you have a 50-gallon tank in a very cold climate and decide you want 300 watts of heating capacity; get two 150w heaters. The rationale for this is simple: it's easier to place them at opposite ends of the system and effect more uniform heating. Also, if you intend to utilize a heater chamber, or a sump, do put at least half your heating capacity in the system tank. Heaters do go out, and even though you might be the prince(ss) of elephantine memory and finesse, they "get" broken. Yes, dear friend and fellow pet-fish sufferer, I have broken many of them myself. I'll 'fess up; some were lifted out, others left exposed when I dropped the water level without unplugging them. Others were stupidly immersed when hot. Enough of my personal heater angst; learn from my errors. Put glass heaters low (but not undergravel) where they won't get diffed by moving decor or irritated big-boy livestock. Put a back-written note on your forehead and a mirror above your system; "Remember to Unplug/Plug in Heaters When Working on Tank". Those of you who are laughing know from experience what I'm getting at.

Cable Heating Systems I wish these things weren't so blasted expensive; they're great and really work well. (See Hamilton and smelt for ideas on a novel approach to building your own sub-gravel heat-exchanger.) Do not try to build your own cable heaters. If I can't dissuade you from trying to make your own, beg of you, at least employ a ground fault interrupter circuit with them--and all heaters.


A water cooling mechanism is necessary for consistently cold water, and for tropical systems that seasonally get to more than 84 degrees F.

Chillers are like miniature refrigerators, capitalizing on the heat lost in controlled expansion/phase change of a refrigerant. Either an emersion coil is placed from the chiller to the system/sump, or more frequently, a heat exchanger serves as a "cold sink" to circulate system water through. In my extensive (and expensive) first-hand experience, the Teflon-coated, copper-bearing units way too often suffer some sort of user, or manufacturer failure; the Teflon gets nicked, a weld wasn't properly done or any of a number of unforeseen problems that lead to systems getting poisoned. I'll vouch for titanium heat-exchangers.

The range in quality, efficiency and average useful lifespan of aquarium chillers is huge. Be leery of all of them. Get literature from several companies and talk with people who are familiar with their chillers as consumers.


 Floating, hanging standing, liquid crystal stick-on types and even electronic units with digital displays from a dollar to hundreds of dollars are available and fine for hobbyist use. As nifty as the digital units are, you don't need a meter of high tech thermocouple to be a good aquarist.

Yes, I know, you can't find two of these less expensive thermometers that give the same reading. They do vary by several degrees, but it really doesn't matter in most instances. All you're really interested in is that the reading is about the same every time.

Are you into keeping records of when, where, how much you paid for livestock, water quality test? Good; add a column for temperature. Want a helpful piece of advice? Get at least two thermometers, three if you have a filter sump, and place them inside the water where you can read them at a glance, and check all three daily. When your favorite blenny dies or your giant clam spews forth eggs and milt, someone will want to know the temperature.

Believe it or not every year I see livestock, sometimes whole systems lost from "thermometer poisoning." No, not from the red-colored alcohol or mercury in them getting into the tank, but from the thermometers themselves. Don't put metal thermometers in your system.

Summary Because our livestock are poikilothermic (cool-cold blooded), and their metabolisms are tied stair-step with the temperature of their environment, it is eminently important that your system's temperature not change much day to day. Changes of more than one degree F a day are rare in large bodies of water like the world's reefs. Thermal stress is all too often a source of environmental weakening of captive livestock, leading to death from other, secondary causes.

Careful temperature control is vital to the success of maintaining a marine system.

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