The Energy Efficient Aquarium


.Cutting Polystyrene

Most aquarists are realizing the cost of electricity used in the hobby, but are less sure how much is used and how to save energy.

 

Electricity is practically the only energy source used in the hobby now. Other types of heating such as gas or kerosene burner, heating the floor of the tanks have been forgotten.

 

Solar heating is the ideal proposition to save energy in the fishroom or the room used for the aquariums in the house. Design and use of solar energy has to be thought of at the beginning of a serious approach to the hobby. Solar heating works strictly on the laws of the sun's movement during the year. Once it has been decided to follow this path there are an infinite number of ways to develop more efficient systems as to energy storage, application of roof panels or even solar cells for direct production of electric current.

 

The basic decision of where to place our tanks in the imperative one. The normal location for the aquariums is in the living area, either free standing or in-built in a cabinet. If the room is heated the aquarium needs less energy than in a non-heated room.

 

Another solution is to have more tanks in a hobby room, but the larger number of fish tanks requires careful consideration s to the heating system. Individual heating of tanks brings high water evaporation and moisture condensation on windows and some other parts of the room. The wholly heated room with no individual tank heaters is the other option.

 

The decision to modify the garage or the ultimate design of a specialised fish or plant room, fulfilling the requirements of the hobby in full, is for the real enthusiast with a long term interest.

 

Now to assess our energy needs to participate in the hobby cheaply. The first thing is to refresh a few basic laws of physics from our high school years.

 

The heat transfer law says that energy moves from high energy potential to low energy potential. Popularly expressed, "warm places cool down". Heat energy is transferred by conduction of the heat through the mass (water, steel etc.) or by convection where the moving air, water etc helps to 'hop' the heat from one wall to the other. The third method of heat transfer is radiation. The glowing heater is an example of radiation. The effects of radiation from low temperature objects is negligible.

 

This is as far as we can go into explanations of heat transfer without getting into the theories of movement of electrons and molecules.

The laws of movement of air and water (the media we are interested in) are simple too. Air tends to rise when heated. The same applies to water. Remember water is heaviest at 4 C (ice floats). Because of this natural law, we experience layering (stratification) of the water in our aquariums according to temperature. The warmest layer is at surface level.

 

Another part of physics creeps into the hobby. Water vapour (humidity) is produced by evaporation of water from the aquarium surface. We do not need to know about relative or absolute humidity of the air, but we should remember the warmer the air, the more moisture it can carry.

 

We can observe moisture from the air condensing on colder surfaces. Here is the human safety risk. Electricity is a dangerous toy. Household electrical wiring carries 240 Volts at a high enough Amperage to kill. The forgotten 12 Volt systems (low voltage, like your car) were too costly, and the cost was multiplied by the necessary use of transformers. Manufacturing companies abandoned production of these safe heaters.

Any electrical installation must be kept out of heavy condensation areas. Switches have to be mounted outside of these areas to prevent the danger of electrical shock.

 

Now we should start to think about different means of saving energy. Savings can be made on any aquarium particularly on free standing tanks. These lose heat from all surfaces. it located in very cold rooms, heating a larger tank can cost up to $30 a month during the peak of winter.

 

In cold rooms the aquarium water stratifies with cold water at the bottom and warmer water at the top. This hides the problems for the bottom dwellers like catfish. The aquarist feels the warmer water at the surface, or takes the temperature with a floating thermometer, and assumes the whole tank is OK.

 

A simple example shows the basics of the process.

 

The aquarium has a temperature of say 24 C. When room temperature is the same, the water is nicely and uniformly warm from top to bottom. During the night or in winter, the room temperature drops to say 16 C or even lower. The air in contact with the side glass gets warmer and starts to rise. This brings cooler air to the glass. This convection (air movement) starts to cool the glass and draws the warmth from the tank. The heat energy dissipates in the room air. The water gets cooler and starts to stratify, cooler at the bottom, warmer at the surface. Heat is also lost from the bottom and the lid but the heat exchange is more complicated particularly when you want to calculate losses accurately.

 

The reverse process starts when the room is heated (or in summer) to a higher temperature than the aquarium water.

 

Let's look at a daily cycle. During the day the temperature is 24 C and at night 16 C. Assume that these temperatures hold for 12 hours each. The aquarium water doesn't reach these extremes. We would expect average tank temperature would be 20 C. This is still OK for the normal healthy tropical fish. But in this case water stratification in the tank occurs naturally and the temperature at the bottom would be drifting down towards 16 ' C, while the surface is above 20 C. This is a clear indication that the temperature measurement must be taken close to the tank floor level.

 

The other requirement is to provide a forced mixing of the water. The simplest method is by aeration or a power filter moving the water and mixing the different temperature layers.

 

To prevent water temperature drop due to a cold environment around the tank we must supply heat energy. The simplest device is the aquarium heater.

 

What output heater is needed for which tank? It can be calculated. We need to know the volume of the tank, the lowest expected temperature, and can then calculate the energy required to heat the water in this case. Then convert the energy units into Watts.

 

A simpler approach, but not as accurate, is to learn from experience. Logic dictates that all gadgets will eventually fall. If you keep very expensive fish 2 less powerful heaters in each tank are a necessity for the water to not get too cold when one fails. For example, a 150 litre tank (4 foot standard) located in an unheated room (facing north) can manage with 2 heaters (15OW). One heater should be set to the lowest required water temperature, say 21 C. The other should operate at the required normal tomperature of say 24 C. This gives your fish a chance of survival when one heater goes 'bust'. The other will keep things OK until you find it.

As a matter of principle it is better to employee less powerful heaters (yet still able to maintain the required temperature level) than the high output ones. Why? The low output heater runs for longer periods, thus is not constantly switching on and off. This frequent switching develops sparks causing the burnout or sticking of the bimetal contacts in the heater thermostat. Lower output heaters don't 'boil' the fishes so easily at least not in a short time.

 

Normal heaters should last at least 5 years or more without problems. But as you know Murphy’s Law is the only one that works perfectly and we get caught very often when we don't expect it.

 

It is a good practice is to put an aeration stone under or near the heater. This helps to move colder water towards the heater (the heater circulates water also by potential water temperature difference). Aeration close to the hotter is essential when keeping Black Mollies who tend to sit on the heater to warm up. When they move into cold water the muscles of the swim bladder tend to cramp up and the fish loses the ability to swim.

 

Until now the article has been devoted to energy input to the aquarium water. Water temperature is one of the most important considerations when keeping tropical fishes. But for the hobbyist the cost of energy used plays an essential role too.

 

We waste most of the energy on heating. The second highest wastage is on lighting the tank. Last comes energy 'spent' on aeration, filters, power pumps etc.

 

How do we handle the heating losses?

 

The first and most important way is to insulate the tank. If we do not utilise the available natural light from all sides and the top of the tank, all sides of the aquarium which are not required for observation should be insulated. One very good insulation is polystyrene sheets attached to aquarium sides. 'Pink Batts' are good but tend to collapse vertically when soaked with water.

 

Polystyrene used under the tank should be increased from the commonly used 12mm to 24 or preferably 36mm thickness.

 

Insulation significantly reduces heat loss. Similar insulation should be a permanent feature of aquariums built into cabinets. The polystyrene advantage is it's soak resistance and easily worked sheets. it also reduces the volume of moist air in air-filled voids between glass and cabinet walls thus reducing the condensation of moisture on the cold surface of the cabinet.

 

Heat loss reduction from lighting is very difficult. For a single aquarium or cabinet the utilization of the lighting heat is unwieldy as the heat is kept above the lid in the vicinity of the light source. There is better utilization of the light - heat energy in vertically arranged aquariums within an enclosure.

 

I prefer to use warmer air for the air pump even when the efficiency dividend is quite small.

 

Saving on lighting is always difficult. Here the use of incandescent bulbs is the worst solution (even though the light spectrum is probably the best for the plants) because 95% of the energy is converted into heat and only 5% forms the light.

 

Neon tubes are more economical but the light spectrum is a nightmare! Working out the balance between GrowLux and daylight tubes, or using the expensive ones such as the Triton tubes, Costs a lot too.

Another path of exploration is the use of the compact fluorescent bulbs (costing $20 - $30 each). 1 have found their light spectrum good for plants, the energy saving is great, and if you avoid overheating in closed hoods they last a long time. The cost is comparable with Triton tubes and the installation is simple.

 

The present design of light hoods is an absolute disgrace! The hoods need to reflect light without bouncing it all over the place.

 

Instead of having a parabolic shape (like a car headlight) the squarish shape of the hoods throw light in all directions. The problem results in a hot hood and light source via ray absorption and loss of light intensity emanated towards the water surface.

 

Utilising the heat energy from the lights with a tiny fan and circulation around the tank would be a major boost to reducing the heating input into the aquarium in winter. In summer the energy for the lights would be wasted for the sake of not overheating the tank.

 

Least of all energy wasters are the various gadgets such as the air pump, water pumps (as filters, power heads etc.). Thanks to the developments of high technology energy consumption is minimal.

 

Air pumps or motorised filters represent energy consumption of 4-8 Watts each. This represents, at the current electricity rate, a cost of 1-2 cents a day. The sophistication and simplicity is so high that the task of saving any more energy is far beyond the scope of the normal hobbyist.

 

We can conclude that there is always room to improve efficiency of energy use in the aquarium hobby. The easiest way is to insulate the tanks and put them into an enclosure (cabinet etc.).

 

Modification of aquarium lighting and use of energy efficient sources is the second step.

 

Reducing the heat loss from the filters and associated pipes can be made by the location of these in areas within the aquarium enclosure.

 

There are other sources of thermal energy which could be used for the hobby. Solar energy with heat accumulation storage is one answer.

 

Room for improvement in energy consumption is quite large and brings not only a savings in dollars but the satisfaction of the personal achievement of saving a little of the world's environment.

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