Optimizing Reef Temperature for Energy Savings

[FileMan44]

I find myself in a somewhat unique situation where my reef aquarium is at virtually no risk of overheating no matter what the season or how much/little I run the heat or air conditioning in my home. My 120 gallon aquarium is located in a dedicated fish room in my basement which naturally stays cool year round. My two, 250 watt heaters maintain a constant reef temperature of 77.7 to 78 degrees. My Neptune Systems controller is programmed to heat with only one heater, reserving the second for supplemental heat if the primary proves inadequate. The Neptune Systems controller and other energy monitoring equipment reveals just how much energy is consumed in heating that tank to what I consider to be a very normal (if anything a lower-end) reef aquarium temperature. The main heater runs at least 50% of the time, often 80% or more. This means my system is pulling almost an almost constant 250 watts just for heat. This all adds up to about 180 kWh's of electricity or almost $15 a month on my region's relatively modest electric prices. As electricity prices are expected to climb sharply over the next year I am beginning to question whether or not I can lower the temperature of my tank thereby saving money. I am only interested in this if doing so won't adversely affect my aquarium inhabitants.

Most everything I have read with regard to reef aquarium temperature centers around people's struggles with keeping temperatures down. This fact seems to be, at least in part, some of the reasoning for people to maintain aquarium temperatures into the 80's. Chillers are both expensive to purchase and operate and I am wondering if many simply have no choice but to run their systems at higher temps. Many sites (i.e. liveaquaria.com) still say safe temperatures go as low as 72 but I have never heard of anyone actually running their systems that low.
Any thoughts?

 

[bertoni]

72 F is not going to be safe as a sustained temperature for a lot of tropical reef animals. I targeted 82 F as the base temperature, but 78 F likely is okay. I lost animals when a heater failed and the temperature dropped into the low 70s or high 60s.

 

[DiscusHeckel]

I have looked at user polls on various forums. Many reefers seem to keep their tanks at 25-26C.

I keep mine between 27-28C. I subscribe to Eric Borneman's school of thought. To quote Borneman: "the reasoning behind maintaining somewhat more natural reef temperatures of 27-29C is that the entire metabolism of the tank is raised, including those of the microbial community, detritus-processing organism, and herbivores." (Aquarium Corals: Selection, Husbandry and Natural History, pp 347-348).

It is also true that there are some negative aspects to increased temperatures. Increasing temperatures above those to which the corals are acclimatised may decrease autotrophic abilities and trigger temperature-induced bleaching or death. However, Eric Borneman directs his readers to anectodal evidence, which suggests that "corals normally kept at 26C may bleach at temperatures above 29C, while those usually maintained at 29C may not bleach until the water exceeds 32C. My own experience during occasional heat waves in summer months in the UK is consistent with this evidence. I have never experienced temperature-induced coral bleaching or death despite the fact that the water temperatures in my present and past tanks reached up to 30C. On one occasion, the water temperature reached at 32C for about 12 hours during a night due to a faulty heater.

 

[thegrun]

I run mine at between 77.2 and 77.5 all winter without a problem. I suspect coral growth will slow a little, but certainly not stop. I know several reef keepers in our local club who let their winter temperatures drop to 75.5 during the winter, including a past RC TOTM recipient.

 

[FileMan44]

How can big sites like liveaquaria.com list temperatures as 72-78. The only time I see any temperature in the 80's recommended its through forums and other independent articles. Is the 72-78 degree mark something left over from decades old predispositions?

 

[disc1]

How can big sites like liveaquaria.com list temperatures as 72-78.

How can they? Simple, when they write their page they just type those numbers in. There's no regulation that says that info has to be accurate. Getting that type of info from the supplier is dangerous in any industry or hobby.

 

[Randy Holmes-Farley]

I heat my tank about 9 months of the year, and cool it for about 3. I target about 80 deg F year round, maybe a little warmer in winter and cooler in summer to account for what might happen in a power failure.

Yes, it is very expensive heating the water.

 

[natas]

You can safely go to 76, this is what I do. My apex is set to turn the heater on at 76.1 and turn it off when it hits 78. It takes around 1.5 hours to do this. Now I understand Randy's philosophy and why he runs hotter in the winter and it is a smart move depending on where you live. Personally I have a generator in case of power issues

In the summer I have my chiller set to start cooling at 81.9 and to stop at 78.6. Don't be afraid of a 2-3 degree swing

 

[FileMan44]

You can safely go to 76, this is what I do. My apex is set to turn the heater on at 76.1 and turn it off when it hits 78. It takes around 1.5 hours to do this. Now I understand Randy's philosophy and why he runs hotter in the winter and it is a smart move depending on where you live. Personally I have a generator in case of power issues

In the summer I have my chiller set to start cooling at 81.9 and to stop at 78.6. Don't be afraid of a 2-3 degree swing

As a ComEd RRTP (Residential Real Time Pricing) participant my energy rate varies every hour based on wholesale market prices "“ a program which has saved me hundreds of dollars a year on electricity. On average, the price I pay for energy is less than flat rate customers and offsetting high energy use appliances to off-peak hours can result in a considerable savings. The trade off for this program is I am exposed to the potential for energy prices to spike during peak hours, especially on extremely hot or cold days. Such spikes in price can be predicted somewhat and trends do exist. In general, summer energy prices are highest from around 2pm thru 7pm. Such large spikes are often offset by deep plunges in energy rates in the overnight hours as excess capacity is dumped by energy providers. On occasion this phenomenon can drive prices into the negative (i.e. the utility pays me to use electricity)

Tying all this back into my aquarium energy savings goal it is possible for me to program my apex to heat more in overnight hours and fall back during the afternoon hours. This however would cause for temperature swings in my system, something I have always made my best effort to avoid.

Can anyone else chime in on natas's statement with regard to allowing the reef's temperature to swing by as much as 3 degrees?

 

[Randy Holmes-Farley]

There are a number of people who think, based on scientific papers, that such swings are actually preferable from the standpoint of making the whole system more rugged toward unexpected temperature rises (like a power failure). I'm not certain it is true, but they had reasonable evidence.

Here's a thread, for example:

http://www.reefcentral.com/forums/showthread.php?t=2130412

 

[dkeller_nc]

A few observations that can make a very large duty-cycle difference (the time the heater stays on):

1. For a typical aquarium, evaporation carries away most of the heat rather than direct conduction, convection and/or radiation from a warm object (your tank) to the cooler surroundings. For example if your tank evaporates 2 gallons of water per day, then that's the equivalent of 200 watts of heating being carried away by the water vapor:

2 gallons/day = 7.75 liters = 7.75 kg/day * 2260 kilojoules/kg = 17,515 kJ/day

17515 kJ/day * 1 day/86400 secs = 0.203 kJ/sec = 203 J/sec = 203 watts

2. It's typically much cheaper to heat with a heat pump or direct combustion furnace (i.e., and oil/gas - fired appliance) than it is with resistance heating.

Based on these observations, you might choose to:

Operate your fish room such that the humidity stays very high, which will drastically reduce evaporation.

Enclose the sump for your tank with foam insulating board (but plumb your skimmer's air intake outside the stand); that will not only reduce evaporation, but will also help hold in the heat from any return pumps or other equipment.

Install a small window-mount heat pump or small ventless natural-gas fired heater and heat the room to 78 deg F rather than the tanks (if you have many tanks that need heating).

Use the Apex's programming capability to reduce the set-point for the temp in your tank from 78 deg F to 76 deg F during the hours of 2-7 p.m. Assuming you've taken steps to reduce heat loss from the aquarium, most large tanks will take several hours to lose a couple of degrees, which might be just enough to avoid the peak utility rate period.