Water - The Environment

Keeping Temperature Under Control

Written by Marina Parha and George J. Reclos Tuesday, 27 July 1999 01:00

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Part I: Dealing with Temperature

It is said that fish keeping is a combination of art, science and skills. Nobody accepts this moto more than me. The scientific part of it guarantees that the rules are the same everywhere and so it is. However, there are some factors that influence our hobby and are, to a great extent, out of our control. These factors are not the same everywhere and have to do with the geographic position of the hobbyist or a particular seasonal condition - especially an extreme one.

Climate & Environmental conditions

The two most common such factors are the climatic and environmental conditions. The environment may be a dusty or a sunny one, the water in a particular region might be polluted (heavy metals, nitrates, ammonia etc.) very hard, soft, alkaline or acidic. In short it may be unsuitable to be used in an aquarium unless a pretreatment stage is involved (if practical) or it may limit the options to very specific groups of fish. Even in the same town the water quality may differ from place to place. However, we can test out tap water and then take counteractions to make it suitable for our tanks. While I was actually reviewing this article I experienced heavy losses in one of my fry tanks because the water company decided to add much more chlorine (or chloramines) in the water.. (adding to the validity of this statement..). In contrast, sometimes we may have to face other factors, which are not under our control. One such parameter is temperature. Temperature normally fluctuates over the year but this is usually within acceptable limits. The problem arises when the temperature becomes extremely high or low. In some places the temperature may reach 110^oF (44^oC) or more in the summer while in other places the temperature may fall well below the freezing point during winter months. Usually these extremes are coupled with the lack of electricity since this is the result of over-consumption or physical damages to the carrying wires. This makes the situation a threatening one and something must be done quickly before losses occur.

Fish Tolerance

Different species show a different tolerance to temperature. Thus, the discus may stand temperatures as high as 34^oC (93^oF) while no goldfish will have a problem in water as cold as 5^oC (41^oF). So the hobbyist should take this into account when selecting which kind of fish he will keep. As for the African Rift Lake cichlids, the Malawi cichlids tolerate higher temperatures better than Tanganyikans. Thus, the Malawians may tolerate a temperature of 32^oC (90^oF) while the Tanganyikans will not tolerate even 30^oC (86^oF). What complicates things more is the fact that Malawi cichlids can also tolerate large water changes (as much as 50%) much better than the Tanganyikan cichlids (less than 25%). Therefore, in a very warm climate, selecting Tanganyicans as the fish to keep is not a wise selection, since you will have very serious problems with high temperature. In such a climate, discus might be a wiser choice. Of course, nothing will stop a dedicated fan of Malawians from keeping them..

Basics of Physics

It is obvious that the problem for the hobbyist is how to change the water temperature of his tank when the environmental conditions "push" it to the wrong direction. Well, the answer is by taking away or giving energy to the water. Before getting to some ideas on how to deal with this problem, I think it would be better to see the theory behind all this. I regard it as essential because this may help you to come up with a much better solution, better suited to your specific need.

1. Heat: the lowest form of energy or a coin you can’t exchange.. Unfortunately, this is true. Energy can't be lost. All you can do with it is change it from one form to another. For example you can change the electric energy to kinetic, or the light energy to electric. However, in every such change there is always a percentage of energy that becomes heat. Heat, in contrast can’t be changed to other forms of energy. So, heat is the "end by-product" of energy changes. Which means that it is silly and costly to change other forms of energy to heat or use other forms of energy to take heat away. Be that as it may, this is what we have to do in order to heat or cool our tank water. So the first point is that we must exchange another form of energy to achieve a transfer of heat to or from our tank water. The next point is that this exchange is not to our pocket's best interests.
2. Water Heat capacity: Here comes point number two - or bad news chapter two. Water has a huge heat capacity. Which is good because it can withstand sudden or temporary changes in the surrounding temperature but it is a real pain when you need to add or take heat away from it. Thus, you need to give one calorie (cal for short, equal to 4,186 Joules) of energy to change the temperature of 1 gram of water (Ok, 1 ml) by one degree Celsius. If you want to do that in one second then you need 4.2 Watts of power (= 4.2 Joules / second). If you have to raise the temperature of your 200 liter tank by 1 degree you need a total of 200.000 cal (or 837.000 Joules). If you want to achieve it in 30 minutes (1800 seconds) you need 465 Joules/ sec or 465 Watt.. A lot of energy. The same energy is required if you want to lower the temperature of your water by 1 degree Celsius. By the way, this is how this "1 Watt per liter" thumb rule for heaters comes in. It is the power that will allow your water to gain 1 degree / hour. This is a bit simplified since it applies to a "closed" system or, in simple words, assumes that the water will not lose or get heat from the environment. The heaters are supposed to be the only heat donator. Usually, we want to keep our water warmer or cooler than the environment so we need even more energy.
3. Water movement: We all know that water movement is essential because we need to increase the gas exchange. Actually, water movement virtually increases the surface of our tank and allows a much greater exchange of gases then still water. This is one side of the coin. The other side is that all this is achieved via a) mechanical parts like power heads, mechanical filters, wave makers etc. or b) by the air released through air stones or other similar items. This is always an additional problem when we want to decrease the temperature of the water because of a high ambient temperature. All this equipment adds heat to the water either because of the motors or because of the hot air that travels through the water column. The increase of the kinetic energy of the water particles is, by itself, a factor that increases the temperature of the water (kinetic energy is finally transformed into heat – see above). Of course we can’t stop water movement (especially when the surrounding temperature is high) as this would result in suffocation, but we have to take this fact into consideration.
4. Solubility and Oxygen solubility: Solubility tells us which is the maximum quantity of a substance that can be dissolved in a specific volume of a liquid at a given temperature. Usually, when we have to dissolve a solid - in water for instance - the higher the temperature the more solid will get dissolved, hence, solubility rises with temperature. Some everyday examples are sugar and cooking salt. However, this general rule is only good for solids. With gases things go the other way around. The higher the temperature, the less gas can stay dissolved in it. As the temperature rises, the gas molecules move faster and faster, finally escaping from the water. And of course, oxygen is a gas.. And the fish need it. So this is another good reason to keep temperature within some limits.
5. Metabolism:This is a term, which describes the chemical reactions that take place in a living organism. There are two kind of reactions : breaking large molecules into smaller ones (catabolism) and building larger molecules from smaller ones (anabolism). As with all chemical reactions, these reactions are temperature dependent. Which means that the higher the temperature the higher the speed of these reactions and vice versa. Fish, unlike humans are cold-blooded animals – they lack a "thermostat". They get the temperature of the water they live in. Which means that at higher temperatures the metabolism is increased which means a greater demand for oxygen - (see above). A direct consequence of an increased rate of metabolism is a shorter life span, a higher level of aggression etc.  In the other end of this, a low temperature means a slower metabolism and – below a certain temperature – death.

These are, in short, the thereabouts of temperature and the implication it could have on our fishes if we don't take any measures. OK, then, what can we do? We only have two cases to discuss: the temperature of the water (and the environment's) is higher or lower than what we want.

Part II: Hot temperatures

Characteristics: Lower oxygen levels, lower carbon dioxide levels. Increased metabolism and aggression, shorter carrying times for the females (especially for mouthbrooding females) and shift in fry sexes are just some of the results. In extreme situations, fish can be seen gasping for oxygen at the water surface or even die of suffocation. What to do? Obviously, cool the water.. How?

Chiller: It is rather expensive but we have to mention it. Well, for those of you who have this kind of money this is the single most effective and reliable solution to this problem.

• Advantages: it will keep your water cooler than the environment for as long as you like, the temperature will not fluctuate and you will just watch your fish while your neighbor has to go with the next option.
• Disadvantages: these devices consume a lot of energy (and we know why) are heavy, very expensive and ugly. They can be used either in line or separately (using their own intake and return pipes). Doesn't work if there is a power failure.

Water changes: This is definitely the way to go for most of us, especially if there are no water restrictions in our area. Water is generally cheap (much cheaper than electric power anyway) and "it takes one to know one". Water is the only thing that can take large amounts of heat from water. Of course, you may have to make daily water changes to keep your water temperature within acceptable limits. For smaller tanks, you may have to make two water changes per day.

• Advantages: Cheap, no equipment needed, effective and safe.
• Disadvantages: not a permanent solution, tiresome, the water chemistry needs to be adjusted all the time, takes too much time, especially if you have many tanks.

Doesn't rely on electricity.

Freezer packs: You know, these plastic things that we take on the beach in special bags to keep our cokes (or beers) cold. They are left in the freezer and then are dropped in the water to cool it. After a short while, you have to take them out and repeat the procedure. Well, actually your freezer plays the role of the chiller and you play the role of the pump.

• Advantages: You save on electricity. Great as an emergency measure for small tanks. Can cool water considerably and save your fish in an instant. An additional advantage is that you don't need to re-adjust the chemistry. Keep the freezer packs clean - preferably use clean bags when placing in the freezer.
• Disadvantages: This is not the way to go for long periods of time or big tanks. Can't be applied if you are not at home all the time to refresh supplies and check the tank temperature (it can remain high or drop substantially). If there are long heat periods it will deprive you of the use of your freezer (particularly if you want to cool down larger tanks).

Ice cubes are somewhere in the middle between water changes and freezer packs - but if you use them you need to watch the chemistry! An alternative to freezer packs is frozen water in bottles. This method doesn't rely on electrical appliances to cool the tank water but you will need electricity to re-freeze your packs or water bottles.

Air conditioner: This is a good alternative especially if you have all your tanks in one room (fishroom or living room). Usually, it is less effective than the chiller (since it has to cool the whole room) but you feel better, too. Since in most cases your fish are not the only creatures that need a cooler temperature, the air condition may be the best overall solution. All the rest being the same, it will make your fishroom the most attractive place in the house.

• Advantages: Cools the whole place, not just water. A heating option is readily available.
• Disadvantages: High consumption; relies on electricity.

Open the covers: This is essential. You have to let the heat escape. If the heat accumulates on the surface of the water, then it will warm the moving surface even more. Evaporation cools the water. If you can increase the rate of evaporation you are actually cooling your water. Definitely the first step you must take. Doesn't need electricity.  Please note that though this is an absolute must it will have an undesirable effect: the water will evaporate which means you may notice some damp in the house (particularly if you have big systems) plus you will need to check your tank regularly for the necessary top-ups.

Ventilators: While you keep the tank covers open, you can also use some ventilators (blowing on the water surface). This removes the water vapours from the surface so more water will evaporate to reach the equilibrium point. Since your ventilators will keep on blowing the water vapors it is obvious that the evaporation will be kept to a maximum so the water will cool. Needs electicity. Please note that you need to secure the ventilators properly to ensure they do not accidentally fall in the tank.

Increase Aeration: This action has a twin effect. By increasing the aeration you are forcing hot air to pass through the relatively cooler water. Since heat is only transferred from the hotter to the cooler body, this action actually increases the temperature of the water. However it also increases the oxygen content of the water (see above). In addition, it increases water surface movement, which, as indicated, is extremely beneficial in cases like this. As the benefits clearly outweight  the risk you are well advised to take this action. Low oxygen content is the number one enemy in hot temperatures. With increased aeration, fish are more likely to stand higher temperatures than usual. If your air pump is located in a compartment under your tank where all the lamp ballasts and heat generating devices are stored, you should remove the air pump to a cooler place or just leave the cabinet doors open. Needs electricity. Please note that this action may not be suitable in some cases, namely for very young fry or fish particularly sensitive to faster water movement. In these cases the hobbyist must look at one of the other alternatives.

Decrease light: Light is a form of energy. As it is reflected on the tank canopy or absorbed by the water it finally becomes - what else - heat. Any kind of lamp (even the fluorescent tubes) will produce heat. There is a number of ways to reduce the heat generated by the lamps. You can decrease the duration of the lighting period (use a timer), or you decrease the number of lamps (you should start by the ones that generate the most heat - metal halides etc.) or finally you can increase the distance betwen the lamps and the surface of the tank. This one doesn’t rely on electricity - in the sense that a blackout will be a favorable thing.

UPS: Since the filters and the air pump must stay "on", it is advisable to have a UPS (Uninterruptible Power Supply) device. If you do, you should only plug the absolutely minimal number of filters and the air pump. Never add heaters, chillers or other energy consuming devices as this will drain the battery in no time. A 1200 W UPS can keep my two filters and the air pump going for at least 3 hours while it will fully recharge in less than 5 minutes. Which means that if electricity comes back periodically, you can practically keep the aquarium running safely for days. Usually, when the temperature is very high people will turn their air condition on. This may cause an overload and cause a black out. During winter months, the same is also true. This time it can be air conditioners, other electrical heaters (e.g. water heaters) or physical damage to the distribution system (too much snow on the wires, storms, etc).

Part III: Low temperatures

Characteristics: Higher oxygen levels, higher carbon dioxide levels. Decreased rate of  metabolism and aggression, considerably longer carrying times for the females (especially for mouthbrooding females), lethargy, fish close to the bottom. In extreme cases death will occur.

Heaters: That's the first thing that springs to mind.

• Advantages: This is the best solution because a) it heats the water gradually, b) the heat is distributed evenly if the heaters are correctly positioned and c) they can keep the water temperature constant. Other advantages are that they are cheap, you can place them anywhere you like (I prefer my filter compartments) and they are practically maintenance - free (although removing accumulated salts or algae will help).
• Disadvantages: Heaters consume too much electricity (it is usually the unit that consumes more than half of the total energy needed to run your tank). Relies on electricity.

Air conditioners: The same as above is true in this case, the only difference being that now the air conditioner will be used in its heating mode. Relies on electricity.

UPS: As already mentioned low temperatures can be accompanied by power blackouts. Although the two methods already mentioned are the ideal ones to keep your water warm, they need electricity. The use of a UPS to support heaters may be the only option however in this case it will be very limited since a 200 W heater will drain the battery within 45 minutes if plugged in on its own. And of course, you can't plug your air conditioner on a UPS, it will not even start.

Fireplace - warm the place: An alternative (in case of a blackout) is to use natural heating resources, like a fireplace. Of course, the tanks should be in the same place with the tanks (neither the fireplace nor the tanks are mobile) and a working chimney is absolutely essential. Never try to heat a place with an open fire. Apart from the danger of starting a fire, the place will be soon saturated with carbon monoxide and dioxide, two [extremely] poisonous gases both for the fish and you. Bear in mind that these two gases do not smell and they will gradually suffocate you.

Fireplace - heat stones / water: Another option is to use your fireplace to heat some water (or rocks) and then add it to your tanks. This option can only be used as an emergency for a small number of small tanks. Heating water is always preferable because of its huge heat capacity.  If you use stones please make sure they are not the normal decorative house stones; they should be tank safe, i.e. not have any varnishes, paint or decorations.

Gas - boil water: If your place has a supply of natural gas you can use it to heat water, which you will have to transfer and add to your tanks. Again of limited use since this will only be feasible for a small number of small tanks except if you have a combi boiler with constant hot water supply. As indicated, you need to add too much hot water to warm a big tank. Surely carrying it in buckets was not your idea of enjoying fish keeping.  Please note that gas supplies do rely on electricity so if there is a power failure your central gas system will not be operational.

As a closing remark to this part we will mention the use of electrical generators. These are the safest back up system for hobbyists having a substantial number of tanks. Generators use petrol to operate and they come in various sizes with different operating capacities (both in duration and load). Although a back system like this is the safest possible solution to power cuts it has some very serious disadvantages. The generator should be placed outside the house in its own installation as it produces toxic fumes and a great deal of noise (which may still adversely affect your neighbours). Petrol is not cheap and depending on the duration of the power cut you may need a serious supply. Remember that your generator will be useless if you haven't got petrol in stock and then again its usefulness will be commeasurate to the amount of petrol you do have in stock. Though there are various models available, the serious ones (which will be able to support tanks effectively) are quite pricey to buy, install and run. Still, for hobbyists with considerable installations and / or hosting rare, expensive or extinct species, this is an option to consider.

Part IV: Calculations - Do it Yourself

As a general rule (to calculate the amount of hot water you need), you have to make some very simple calculations. Each ml of water needs to give or take 1 cal in order to change its temperature by 1 degree Celsius.

• How much water do I have in my tank? Each liter is 1000 ml.
• What is the temperature of this water? Let's say 20^oC.
• How much do I want to heat it? Let's say you want to raise the temperature by 5^oC.

In this case, every ml of your water needs 5 cal, or 5000 cals in all for each liter.

If you heated water to 100^oC (boiling water) then, each ml of the boiling water will give you 75 cal before reaching the temperature of 25^oC where no more heat exchange can occur. Thus, in order to get the 5000 cals you will need 67 ml of boiling water for each liter in your tank. For an 100 liter tank you will need 6,7 liters of boiling water. The result will be 106,7 liters of water with a temperature of 25^oC.

Ok, don't panic - not yet.. It is quite easy. V_add is the volume you have to add. You want to find it isn't it? V_initial is the volume of the water you want to heat (your tank). Both volumes should be expressed in the same units; both should be expressed either in ml or in gallons, liters or whatever. Up to now there is nothing you can't do.

ΔT₁ is the difference in degrees (F or C) between the temperature of your water in the tank and the temperature you want it to reach. If your water has a temperature of 20^oC and you want it to reach 25^oC then this ΔT₁ is 5. Even if you want to cool your water (from 25^oC to 20^oC) the result is still 5 (not -5; it is the difference that matters not whether it is up or down). ΔT₂ is the difference between the temperature of the water you heated and the temperature you want your tank water to reach. If you heated your water to 100^oC and you want your tank water to reach 25^oC then this number is 75. Then you just do the calculations. It doesn't matter if you use ^oF instead. Again you have to use either ^oC or ^oF in the formula, not both.

NB: The scientific part of our discussion in this article is rather simplified as our aim has been to allow the maximum number of hobbyists to access the information. Hopefully  the simplifications will not annoy specialists. Comments, corrections and/or amendments are, as always, welcome.

 

 

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