It's that time of year again, and the aquarium
thermometers are starting to rise. If this is the first summer
your aquarium has seen, or if perhaps you have upgraded the
aquarium's lighting since last summer, you might be finding
yourself in a predicament - the aquarium is too hot. There
are numerous ways to cool an aquarium, they range from the
simple and inexpensive, to high tech and pricey options, all
depending on how severe the aquarium's heat issue is. Even
if your aquarium's temperature is just slightly warmer than
optimal, there are a few simple things you can do to bring
it down a degree or two.
The primary methods of aquarium cooling
fall under these five basic categories:
Simple fans that run on a timer along with the lighting
· Fans regulated by
simple temperature controllers
· Thermoelectric chillers
· Refrigerant based
· Alternative methods
Most aquarium literature will state that
marine aquariums should be kept between 75° to 82°
F, and this is the range that will be addressed. It is important
to understand that each situation is different and the temperature
of an aquarium depends on many factors including: the size
and shape of the aquarium, the ambient room temperature, the
type of lighting, the distance of the lighting from the water's
surface, the presence of large water pumps, and the surface
water movement of the aquarium.
With so many factors affecting water temperature,
it may be necessary to "experiment" with various
cooling options to find one that works best for your system.
Before taking action to counteract a heat related problem,
perform a check of your aquarium system and make sure nothing
is malfunctioning or incorrectly configured. Is the heater
set at the right temperature? Is the thermometer you are basing
your aquarium's temperature reading on a high quality device?
Many consider the very inexpensive floating glass aquarium
thermometers unreliable. It seems that electronic thermometers
like those on Ranco controllers are usually accurate. Are
the powerheads functioning normally with their output directed
One common source of heat in our aquariums
is powerful lighting. Accordingly, the light fixture, canopy,
or hood where the lighting is located is the "hot spot"
that will be discussed first. For this factor, fans that are
run on a timer with the lighting and fans that run on temperature
controllers which turn them on when the temperature gets too
hot are useful.
For a strip light fixture resting directly
on a glass top, a simple medium-sized tabletop fan mounted
so that it blows air across the light fixture may take care
of any heat problems. If a tabletop fan can't relieve the
heat, raising the strip light up an inch or so by placing
small blocks of wood under each end may assist in lowering
the temperature. Caution must be used here - the author is
making the assumption that most strip lights contain either
normal output (NO) fluorescent or compact fluorescent bulbs.
If wooden blocks are necessary to permanently prop up the
light fixture, they may be painted to match the strip light
or the aquarium's trim. I recommend using paint marketed for
the exteriors of outdoor cooking grills. This paint can handle
high temperatures and, to an extent, exposure to saltwater.
If your aquarium has a wooden hood or canopy
that houses the lighting and has a heat problem, there are
a few options. Glass tops over tanks reduce the amount of
water that can evaporate and thereby increase the temperature
of the aquarium. Removing the top may be a quick solution.
If there is a concern about the animals jumping out of the
aquarium, eggcrate available at hardware stores can be used
to cover the top of the aquarium or the open back of the aquarium.
If the heat problem isn't being caused by the greenhouse effect,
try using fans to ventilate the hood.
You can find DC (Direct Current) fans (the
kind used to cool computers and electronics) and the AC (Alternating
Current) adaptors necessary to run them inexpensively from
numerous reputable dealers. Computer websites like Xoxide
have a large selection of DC fans that work well. Note that
attaching one of these fans to an AC adapter will require
some electrical knowledge. Direct current fans that move air
at speeds of around 85 cfm (cubic feet per minute) are available
for around $10, and AC adapters can be found for less than
Andrew Trevor-Jones (ATJ) uses a medium-sized tabletop fan
mounted so that it blows air
across the metal halide lamps and the water's surface on his
50 gallon reef.
Photo courtesy of Andrew Trevor-Jones.
Alternating current (AC) fans that move
85 cfm are available from electronics stores such as Radio
Shack. The advantage of this kind of fan is that an AC adapter
(which takes up a lot of space on a power strip and may be
difficult to connect) is not required. The disadvantage of
this kind of fan is that it uses more electricity to run than
the smaller voltage DC fans. Some aquarists also recycle fans
from old appliances or use tabletop fans, depending on how
much space they have behind their stand or hood.
More important than the type of
fan used is the manner in which the fans are positioned.
Fans can be used to either blow cool air into a hood or pull
cool air into and through the hood (blowing out air that has
warmed as it passed through the canopy). Usually, fans are
not best applied to pull air through the canopy unless it
is nearly sealed except for an inlet for fresh air. This method
can be useful, however, when the primary lighting is between
the fan and the hole. As an example, the author has a 15 gallon
propagation tank that has an 85 cfm fan located at one end
of the canopy and five 3/4" vent holes (in a nice symmetrical
pattern) on the other side. The canopy is sealed all the way
around except for a rectangular cut in the back, which fits
perfectly around the filter. Lighting is provided by a single
250 watt metal halide bulb (it didn't seem like overkill at
the time!) and two 13 watt actinics. Despite the large wattage
on such a small tank, there are no heat problems as the fan
gently draws air past the metal halide bulb and out of the
canopy. I have heard that temperature variations caused by
a lot of air flow on or around a metal halide bulb could be
detrimental to its spectral output. Hello Lights, a popular
aquarium lighting company, kindly assisted me and researched
the issue of air flow on and around the bulb in the IES Reference
Manual. The manual stated, "With HID equipment [such
as metal halide], temperature variations have practically
no effect on light output." In order to affect the light
output the arc tube's temperature would have to be changed,
and since the arc tube is running at such high temperatures,
any ambient temperature variations are negligible. The bottom
line: unless you are blowing a huge fan right on the metal
halide bulb, you will not affect its function or damage it.
The author (kmk2307) designed this closed canopy to draw air
past the metal halide bulb and
of the canopy. Although it is a powerful light on a small
aquarium, there are no heat problems.
When a fan is used to pull air through
a canopy, it is being exposed to a lot of warm, humid and
salty air which may reduce its lifespan. It is advisable to
check fans used in this type of application frequently to
be sure they are not becoming "clogged up" by debris
like dust or salt. In canopies with an open back, a fan blowing
cool air into the hood will cause heated air to flow out,
thus keeping the hood cool. Fans used in this application
should be fitted with an intake filter, which is usually made
out of a type of synthetic sponge so that dust is not being
blown into the aquarium.
Marc Levenson (melev) uses an AC fan directed at the water
surface on the sump of
his 29 gallon aquarium. The fan promotes
evaporation, and thus cools the aquarium.
Photos courtesy of Marc Levenson.
When your coffee, tea, or soup is too hot,
you blow on it and it cools it down. The same principle can
be applied to an aquarium. Fans may be used to increase evaporation,
thereby causing an aquarium to cool down. A fan mounted at
an angle or completely horizontal blowing on the water surface
can decrease the temperature of the aquarium significantly.
Keep in mind that if a lot of water evaporates from the aquarium,
the salinity of the water will increase. Since evaporation
has such a cooling effect on an aquarium, it is common sense
that an aquarium with a small amount of surface area might
be more difficult to keep cool. Powerheads can also be used
to agitate the water surface of the aquarium and cause evaporation.
One final note on fans: an aquarium whose heat is controlled
by only one fan may be subject to a catastrophe if it were
to fail. I speak from experience!
Another inexpensive alternative is an electronic
temperature controller. Ranco makes a model that is commonly
used with reef tanks. This type of controller can be set to
act like a temperature-controlled light switch. When the tank
water gets to a preset temperature (let's say 82º F),
the controller turns the lights off. After the tank water
cools to another preset temperature (let's say 80º F),
the controller turns the lights back on. A controller of this
type can be an effective backup to fans. The cost of this
type controller typically is in the $70-$100 range. The built-in
digital thermometer is also a nice feature that can be used
as your primary or secondary thermometer.
If you've tried using fans and controllers
to reduce the temperature of your aquarium to no avail, the
next step in aquarium cooling may be required - a thermoelectric
chiller. Thermoelectric devices, like air conditioners, are
based on "The Peltier Effect." According to EIC
Solutions Inc., "It [The Peltier Effect] utilizes two
elements of a semi-conductor which is constructed from doped
Bismuth Telluride. Upon application of a direct current (DC)
power source, these devices generate a cooling action, countered
by a generation of heat on the opposite side of the device."
Although aquarium thermoelectric chillers may function slightly
different than the products by EIC, they are still based on
the same principle. Thermoelectric chillers are usually either
in-line or devices mounted into the aquarium through bulkheads.
The two most commonly seen thermoelectric chillers are the
(below left) and the AZOO Thermoelectric Heater/Chiller
If you have severe heat problems, you may
need to look into getting a Freon or other refrigerant-based
chiller. Liquid refrigerant-based chillers are extremely useful
in decreasing the temperature of aquariums. The problem with
these devices is that they are extremely expensive and use
significant amounts of electricity. Liquid coolant chillers
can be either "in-line," or a "drop-in coil"
type. With an in-line chiller, water from the aquarium is
pumped through it and returned to the aquarium or sump. A
drop-in coil has a metal coil (with lots of surface area)
that is placed in the sump and cools the aquarium. Chillers
range in sizes from around one-quarter horsepower to greater
than 1 horsepower. Some liquid coolant chillers have other
features like digital thermometers and heaters built in.
Whenever one engages in a "do it yourself"
(DIY) project, safety must be kept in mind at all times. Please
be careful and logical when working with electricity, especially
when it will be used around water! If you are unsure about
something get advice from an expert or better yet, have an
expert do it for you. Some fans have metal blades and do not
come with any sort of cover or screen. Be careful not to put
your fingers or other body parts into them. Also, if children
could be around the aquarium, keep in mind the potential hazard
created by sharp fan blades. Galvanized screen that can be
used to cover the blades of some types of fans is available
from hardware stores. Keep in mind that unless it is specifically
stated in the product's literature, most fans aren't designed
to get wet or be exposed to saltwater. Also keep in mind,
saltwater is very conductive of electricity so proper grounding
of electrical devices is essential. I use and recommend a
ground fault circuit interrupter for all my aquarium devices.
To summarize, marine aquariums are prone
to heat problems due to powerful lighting and heat produced
by other equipment like water pumps. A tabletop fan can be
aimed at a striplight to keep it cool and keep heat out of
the aquarium. Glass tops create a mini greenhouse effect in
the aquarium and keep water from evaporating, thus keeping
heat within the aquarium. A possible substitute for a glass
top is a fitted sheet of eggcrate which is available at most
hardware stores. Small fans such as the kind used to cool
computers can be mounted in a custom hood to either pull heat
out or push cool air into it. Some fans, like those by Icecap,
have sensors that vary their speed based on the temperature
inside of the hood; the hotter the temperature, the faster
the fan runs. Alternatively, lights can be put on a controller
like a Ranco model that turns them off when the temperature
rises to a preset point. When the temperature drops to another
preset point, the controller turns the lighting back on. Thermoelectric
chillers provide benefits similar to that of a liquid coolant
based chiller at a much lower cost. These thermoelectric chillers,
however, are not nearly as powerful as liquid coolant chillers,
and in some cases are too weak to remove enough heat from
the aquarium. Liquid coolant chillers, although somewhat expensive,
are the ultimate in aquarium heat remediation. These chillers
use liquid coolants like Freon to counteract excess heat in
an aquarium. If you are experiencing problems with heat in
your marine aquarium, hopefully this article will give you
some ideas on how to rectify them.