Do tropical aquarium need a heater?

rohnds

Large Fish
Apr 23, 2005
408
1
0
Austin, TX (born NYC)
#1
Title: Do tropical aquarium need a heater?
Author: Rohn DeSilva
Date: Dec 8th 2008

I have been asked numerous times if a heater is absolutely necessary for a tropical fish tank. My answer is no. But many experts advise on getting heater and setting the temperature at specific setting. According to these experts water temperature need to at a constant without fluctuation to prevent temperature shock. This argument is scientifically nonfactual. I will explain why.



I have a database consisting of more than 60,000 species of tropical fishes. From this database, the average minimum and maximum temperature after normalizing the curve is 46°F and 101°F.

What does this mean. If you look at any profile of any type of fish, they list temperature range which the specific fish can survive. The temperature is usually listed as minimum and maximum. The reason for this lower and upper bound is to reflect the temperature condition of their natural environment.

Guppies are one of the most common and widely kept aquarium fishes. They are easy to keep and can survive under adverse condition. So I am going to use this species to illustrate my point. The most conservative temperature limit for million guppies are 62°F and 86°F. The native environment for these fishes are the swamps of South America where the water depth is a mere few meters. To my knowledge these swamps are not installed with heater kept at constant temperature. Thus temperature of the swarm fluctuate between 62°F and 86°F. In the day time the water is heated and during the night the water temperature falls. This high and low temperatures are what is given in most profiles. And in this case it is 62°F and 86°F.

Can this temperature fluctuation cause temperature shock? The simply answer is no. This fluctuation take place over 24 hour period at a slow rate. The water temperature doesn't jump from 62°F to 86°F or fall from 86°F to 62°F in few minutes. It happens gradually as the sun goes down and the air temperature cools down, and thus effecting the water temperature.

How does this effect your aquarium. Before I go on to explain this, I am going to give you a brief explanation of the thermodynamic of water. In nature, water temperature of a body of water is dictated by either internal or external. Internal causation is where the water is heated by geothermally. While external causation is when the water temperature is effect by the air temperature. We can rule out the first since guppies (and most tropical aquarium fishes) do not live in such conditions. Thus we can look at the effect of water temperature due to air temperature more closely since that is the main causation.




There was a temperature versus depth study done by UCLA. The temperature was measured by bathythermograph. The experiment was conducted when the air temperature was 18°C and thus the graph intersect the y-axis (or Temperature) at 18°C (64.4°F). Therefore at the surface water, temperature is identical to the air temperature (i.e depth of 0 meters).

The temperature versus depth graph is a linear till about 125m and then logarithmic further down. According to this data, temperature decrease of 7.8°C or 46.06°F occur at a depth of 125 meters. The temperature drop till this depth (125M) is has linear coefficient such that for every 1 meter depth, a temperature drop of 0.36848°F is observed. But the temperature drop beyond this point is dictated by complex exponential function.

This experiment was conducted for large body of water and the source of light as the sun. Compared to this, our aquarium are very small and thus have direct impact and higher correlation with the air or room temperature. And thus we can assume that water in an aquarium will be only slightly different from that of the air temperature or the room temperature. And since the water in our aquarium is effected by the external light from all four side, the temperature of the water remain stable and close to the surface temperature as possible. When I measure the temperature of water in aquariums with various height, I came to data closely resembling the UCLA project.


So if you we are keeping guppies in a 55 gallon tank and the air temperature is 75°F, then the temperature drop at the bottom of the tank is only about 74.6°F. Since our guppies can tolerated temperature as low as 62°F, then our guppies will be perfectly fine provided that the room temperature doesn't drop below 62.4°F during the night. Conversely they will be perfectly fine, provided the room temperature doesn't rise more than 86.4°F. In most homes where majority of aquariums are, the room temperature only fluctuate between 85°F during the day and 75°F during the night in the USA. The constant temperature is maintained by us either using our AC or heaters. And thus if you have tropical fish that can survive in the temperature range between 74.6°F and 85.4°F, you do not need a aquarium heater.

Conclusion:
Provided that the room temperature doesn't fall +0.4°F below the low limit and
rise above the -0.4°F the upper limit, you can keep a tropical aquarium without heater.
 

logtail

Medium Fish
Mar 10, 2008
79
0
0
#2
Yeah well some people don't keep their houses at 75 degrees as this is a waste of energy. Hence a heater in a tropical tank. Also, fish seem to be more active at a more constant "tropical temperature" of 78 degrees or so. This is desireable amongst people who have fish and actually like to look at them. The data is there and seems factual, but in practice probably no one will take this as sagely advice.
 

unwritten law

Superstar Fish
Sep 2, 2008
1,471
0
0
33
DC
#3
Didn't someone have some zebra plecos on this site that died because their heater broke? I mean guppies are like tanks.... like rabbit tanks, the reproduce a lot and nothing can kill them beside an Oscar but a lot of fish probably do need a heater because they do live where water temperature is pretty constant.

Where guppies live, the water temperature drops that much, which means that the air temperature is dropping A LOT too. Since water has a higher specific heat than air, it takes more energy to raise or lower the temperature of water compared to air. So if the water temperature is dropping 24 degrees in a day then the air temperature is dropping a lot more, save that is the only influence on the water temperature.

I do believe you that guppies and some tropical fish can live without a heater but I think a constant temperature would be less stressful, even if the temperature change is over a long period of time. I am more biased though because my house doesn't have heat right now, damn landlords, and I sure am happy I got a heater in my tank or they would be much more than lower than the lower limit
 

Chris_A

Large Fish
Oct 14, 2008
615
0
0
Edmonton, Alberta, Canada
#4
The largest problem is the stability... Absolutely most temp shifts are slow and do not shock the fish... BUT they do stress them over the long term.

While I didn't notice anything "glaringly wrong" with that little artical it does kind of concern me... idk, almost like it gives and "out" for lack of a better term.

There is also another issue though. How is there that much of a temp difference over the hight of aquariums? Merely having a filter or air pump going should keep the tank fairly homogenous and prevent stratification in such a small area.

Chris
 

Jun 21, 2008
493
0
0
#5
I'm not sure how relevant this is, but people can live without air conditioning in Texas, but that doesn't mean that you're going to be anything less than miserable during July and August. Also, aren't wild strains normally more hardy than tank bred strains? Tank bred fish are used to having the temperature constant, and it seems like they would thrive best in parameters close to what they were bred in. Also, why not just invest the $20 to $50 to get a heater rather than make the argument that they'll be fine. In the world of fish keeping, it's a relatively small investment. I know my house frequently gets colder than 75 degrees during the winter, and even if it doesn't, a small investment keeps all your fish from dying if the house heater breaks while you're gone. I just don't understand why you would not do it, even if you could.
 

iapetus

Large Fish
Jan 15, 2008
572
0
0
34:09:39N, 118:08:19W
#6
I'm of the same opinion as Chris and unwritten law. Most of the OP strikes me as not generally incorrect. And, I suspect that you could get by without a heater. I don't think the fish would be happy, but they'd get by.

However, this is the paragraph with which I would take issue:
This experiment was conducted for large body of water and the source of light as the sun. Compared to this, our aquarium are very small and thus have direct impact and higher correlation with the air or room temperature. And thus we can assume that water in an aquarium will be only slightly different from that of the air temperature or the room temperature. And since the water in our aquarium is effected by the external light from all four side, the temperature of the water remain stable and close to the surface temperature as possible.
Everything that is pointed out here argues, IMO, for the use of a heater, not against one. Aquaria are small. And, they do radiate heat from (generally) at least four or five sides. Therefore, they are subject to much larger and much faster temperature swings than larger bodies of water found outside the home. And, if you live in a cold winter climate and your tank is near an exterior wall, you're only increasing the temperature swings to which the tank is subject.

Finally, there's one more point that the OP doesn't really address: fish are mobile. I have to wonder (though I really don't know) whether fish tend to vary their depth in order to moderate the temperature of the water they're in. That is to say, fish in the wild swim to water they find to be at a comfortable temperature. They don't have that option in our homes.
 

homebunnyj

Superstar Fish
Jul 13, 2005
1,299
4
0
Western NC
#7
WB, rohnds! Anther interesting post! It has been a little slow around here.

You guys know rohnds, right?




Well, if not, you can get acquainted with a forum member by looking through their old posts. ;)
 

Kalavek

Large Fish
Aug 2, 2008
169
0
0
Vancouver BC
#8
Just something to point out, not that I'm taking sides or anything - this is coming from both sides of the argument

1) I'll grant that many fish won't have an issue with a temperature that varies between day and night - however just about everyone has jumped on this as strictly a heater/no heater thing. I think it's more about simulating a natural temperature profile, rather than making your fish follow your temperature profile. Your fish tank is not a lake! You cannot expect the ambient temperature drift in your tank to match that of a massive body of water.

I'll take the idea one step further by suggesting two heaters: the first one is set at your nighttime temperature minimum (say 72 degrees), while the second one is set up on a timer (similar or matching time to your lights) and set to 75 degrees. Thus days are warmer than nights, and your room temperature is irrelevant as long as your room temperature doesn't exceed 72 degrees. (This is just for example. You'd have to research the natural environment of your own fish and go from there.)

2) ON THE OTHER HAND, I have to agree with what others have said: your fish are not likely to complain about a constant temperature, unless you've got some sensitive species with breeding in mind. Sure, everything in the natural world accepts cold nights and warm days, but if I had a choice I would totally go with a constant, comfortable temperature 24/7. I want my fish to always be comfortable, so my own tank is always between 75 and 76 degrees.

But if I did choose to do a temperature cycle, I would control it - not ignore it.
 

#12
I appreciate all of your research. It seems like you did a lot of work.
If you are able to keep stable and appropriate temperatures in your house then you don't need a heater. This is true. But if you want to keep the temperature of the water at true tropical temps then you are either going to need to purchase a heater, or be pretty hot all the time.

Also, if the temp in your house does fluctuate (I've got a programmable thermostat which allows the temp to drop quite a bit in the evening) then you're going to have problems. It's true that in nature water temp will go up for 12 hours and then down for 12 hours. But in an aquarium the water volume is so much lower that the change occurs much faster, and can cause shock.

Unless you're keeping goldfish, or White Clouds is better to have a heater.
 

rohnds

Large Fish
Apr 23, 2005
408
1
0
Austin, TX (born NYC)
#13
First, I would like to thank everyone for their constructive criticism. It is highly welcome.

I would like clarify a point. The article was written not with the comfort of the fish in mind but rather their health and well been. Just like any species of animal , they can withstand adversity. If they cannot their species is doom for extinction. Survival in adverse condition is a must.

Some suggest that a aquarium is effected from all 6 sides unlike a lake. This was taken into account when the readings were taken. This clearly stated in the article. The fact remain there is only a 0.4°F temperature drop per meter of depth till the what I called the "stability point" (lack of a better word) is reached at 125m.

I live in Austin, TX. It is true that in the middle of summer the outside temperature can reach as high as 105°F. But in almost all houses and apartments the air conditioning keep the temperature between 75°F and 85°F.

The same applies in Northern state during winter. Having the aquarium next to wall doesn't have a drastic effect. This is because temperature gradient between the middle of the room and the wall cannot be more than a few degree.

All this useless if decide to keep the room temperature at 105°F during the summer and 50°F in the winter. Then I would definitely put in a heater.
 

rohnds

Large Fish
Apr 23, 2005
408
1
0
Austin, TX (born NYC)
#14
I also like to respond to the statement that fish are more active at constant temperature.

Fishes are cold blooded animals. That is they are unable to control their body temperature to maintain a desired heat level.

As I stated earlier almost all fishes have temperature range in which they can survive. If the temperature fall below the low limit, then their activeness is reduced since their body temperature will reflect the water temperature. This is because at low temperature, their metabolism slows down and thus their energy level is reduce. For this reason animals (fish in this case) will become less active to reeves their energy for vital functions of their body.

When the water temperature rises beyond the upper limit, then the opposite is true. With increase in body temperature, vital organs functions faster and thus increase the energy level. With increase in energy level their active rise to release some of the excess energy.

So a fish at constant temperature is not more active than one at higher temperature.

The conclusion is that fishes can handle range of temperature without effecting the well being of their health.
 

iapetus

Large Fish
Jan 15, 2008
572
0
0
34:09:39N, 118:08:19W
#16
This high and low temperatures are what is given in most profiles. And in this case it is 62°F and 86°F.
Y'know, I was thinking a little more about this. I'm also not sure that these numbers are the right ones to use for the water temperature in the tropics. To begin with, water has a much higher heat capacity, which means that it responds to external forcing much more slowly than air does. This lag will necessarily result in lower deviations about the mean temperature. In other words, it will take much longer for water to heat up, say 24°F, than it would for air. And, by the time the water would have heated up to that degree, the Sun has dropped in the sky and can no longer heat the water to that degree. Therefore, whereas air temperature might fluctuate 24°F in a day, the water can't fluctuate by the same amount. So, it's not at all clear to me that this large swing is something that tropical fish actually experience in the wild.

Furthermore, I looked up the monthly temperature averages for Manaus, Brazil on weather.com. As you can see, the average high in Manaus is somewhere between 86°F and 90°F; the average low is between 72°F and 74°F. A swing of 24°F is large even for the air temperature.

The same applies in Northern state during winter. Having the aquarium next to wall doesn't have a drastic effect. This is because temperature gradient between the middle of the room and the wall cannot be more than a few degree.
Yeah, I dunno. Even in heated rooms Up North during the winter, the windows can be pretty cold. Just put your hands against the glass. So, if your tank is on a stand, particularly a metal one, that is in contact with the wall and/or near a window, I would think that could actually have a significant effect on the tank temperature.

(PS - I just pulled Manaus out of the figurative hat as a tropical city. I just looked up the numbers for Singapore, Singapore (after all, not all of us keep just South American fish ;)). The variation in temperatures is even less!)
 

Chris_A

Large Fish
Oct 14, 2008
615
0
0
Edmonton, Alberta, Canada
#17
Y'know, I was thinking a little more about this. I'm also not sure that these numbers are the right ones to use for the water temperature in the tropics. To begin with, water has a much higher heat capacity, which means that it responds to external forcing much more slowly than air does. This lag will necessarily result in lower deviations about the mean temperature. In other words, it will take much longer for water to heat up, say 24°F, than it would for air. And, by the time the water would have heated up to that degree, the Sun has dropped in the sky and can no longer heat the water to that degree. Therefore, whereas air temperature might fluctuate 24°F in a day, the water can't fluctuate by the same amount. So, it's not at all clear to me that this large swing is something that tropical fish actually experience in the wild.
Bingo! That higher Specific Heat Capacity is a big factor. Same with Thermal Mass and in deep bodies of water Thermal Stratification. All those things combined mean that most bodies of water have a relatively stable temp.

Chris
 

Avalon

Superstar Fish
Oct 22, 2002
2,846
10
0
Ft. Worth, TX
www.davidressel.com
#19
I can tell you from experience that temperature fluctuations that occur naturally, as opposed to the fluctuations that occur from water changes et al, aren't harmful to fish. I tend to disdain the use of heaters due to the extra power cords, extra stuff in the tank, and energy drain. During the warmer months, I don't use them. During the winter, I keep the household temps much cooler because I'm adapted to cold temperatures and at icebox temps for sleeping. While I could leave the heaters out, work allows me to turn off the heater while I'm at work, and temperatures can get downright cold at times. I know my fish can handle them, but I prefer to keep the tank at a constant temperature because of my smaller tank. With a larger tank, I probably wouldn't worry about it as much.

My main point is that I agree with the article, but when dealing with large bodies of water vs. small aquariums, small aquariums can deviate in temperature much faster than larger aquariums (or bodies of water), particularly when the ambient air temperature is already low. My best advice and only suggestion would be to use common sense. Fish are tougher than you think, but if you keep low temps like me, a heater may do you well. In most cases, heaters really aren't necessary.