How to calculate running costs of a large tank

[Kodski]

I'm looking into planning a large aquarium build. The smallest I'd like to go is 400 gallons and potentially all the way up to around 1200-1500 gallons. What very well could be the limiting factor however, isn't the actual volume of water. I'm thinking my limiting factor will be running cost. I'm not worried about equipment cost and startup costs, as I can always DIY, buy used, or save up. That does no good though, if in the end, I get everything up and running just to find out that my pocketbook isn't up to the task of supporting that large of a tank let alone enough of a budget left over afterwards to actually put a living animal in the tank. So being one that likes to research and plan things out, that brings me to the question of, how does one calculate running costs of a large tank?

Of course you have consumables like salt, filter socks, filters, light bulbs, ect, all of which are fixed enough to at least calculate based on water volume, water change plan, and length of running time. But then you have things like, calcium dosing, alk dosing, that are all variable tank to tank. You've also got your literal consumables, all your fish food, how does one at least come up with a rough cost estimate for all of these?

Then there is power. Again, you've got the easy things to calculate like return pumps, powerheads, skimmer, ect. Using wattage and estimated run time you can figure out running costs that way. But how does one calculate the cost to actually heat such a volume of water? Figure out the ambient temperature difference vs the desired temp, then somehow figure out the thermal heat transfer efficiency of whatever heating method I go with? Is that even possible? Or what about humidity control, on large tanks humidity is always a concern and we all know it sure costs enough to keep our house comfortable, let alone having several hundred gallons of water to worry about as well.


I understand for a small tank, running costs are just part of owning a tank, and if you're worried about the running costs there that you've probably chosen the wrong hobby. However, I have got to imagine that at some point there has to be some kind of regard and planning to upkeep costs in relationship to the size of the tank. I mean, some of the large tanks home to Reef2Reef have got to cost several hundred if not thousands of dollars a month to maintain and keep running. I personally just want to figure out where my limit is BEFORE I go through the trouble of planning a tank that ends up being too large for me, er.. my wallet to support.

 

[CookieRdReef]

Guess how much it might cost, then add a zero to the end of the number.

 

[Kodski]

Guess how much it might cost, then add a zero to the end of the number.

Figured I'd get a comment like this. Please refer to my last paragraph. From a financially responsible view point, running a large tank is a big undertaking. I'm sure your comment is in good fun, but realistically, you wouldn't buy a Ferrari without first knowing the cost to maintain it.

 

[Lbrdsoxfan]

I'm in the mindset of if you are worried about the cost, probably not a good idea for you.

My electricity cost alone to keep both of my tanks lit up and pumps running are between 70-90$ alone a month and my total water volume is half of 400 gal. Electric cost is higher in the winter since I keep the house in the high 60's, temp wise.

My fathers tank is a 210 with a 90g sump, I know it's at least a few hundred dollars a month+ to keep it running between electricity, occasional water changes usually every 3 months or so, rodi water cost for top off, salt and food cost. Winter is even more expensive with electric cost due to the heaters running, a total of 900 watts if all 3 heaters kicks on (rarely).

You gotta do your own math for your situation. Too many variables for it.

 

[CookieRdReef]

Figured I'd get a comment like this. Please refer to my last paragraph. From a financially responsible view point, running a large tank is a big undertaking. I'm sure your comment is in good fun, but realistically, you wouldn't buy a Ferrari without first knowing the cost to maintain it.

Yes it wasnt a helpful comment, I would love to run a giant tank one day, I hope tou can make it happen.

 

[CookieRdReef]

On a not sarcastic note, fish only would save a lot of $$. No lights, much easier maintenance I assume, no dosing. Plus no spending way too much on corals. Big angels, lots of butterflyfish, a couple puffers would be a sweet tank.

 

[Kodski]

See that first sentence has me frustrated because I feel like that’s the only answer you get to this question. (No offense) it’s a stupid answer, because how can any responsible adult just brush such a significant cost under the rug? A car guy doesn’t just go, we’ll if I’m worried about the cost of premium gas I guess I better not buy a car. They plan accordingly and buy a vehicle they can afford.

to your second point, that is exactly my question. With so many different variables, how can you even estimate something like heating costs. There has got to be a way to get at least a rough number based on how much water you have to heat versus the number of degrees above ambient temperature you need to heat it.

 

[Kodski]

On a not sarcastic note, fish only would save a lot of $$. No lights, much easier maintenance I assume, no dosing. Plus no spending way too much on corals. Big angels, lots of butterflyfish, a couple puffers would be a sweet tank.

Unfortunately not something I’d ever dedicate that large of a space to. Lol for me it’s gotta be a reef.

 

[davidcalgary29]

to your second point, that is exactly my question. With so many different variables, how can you even estimate something like heating costs. There has got to be a way to get at least a rough number based on how much water you have to heat versus the number of degrees above ambient temperature you need to heat it.

The best way to start your calculations may well be to negotiate a fixed term contract with your utilities. Variable rate contracts are going to WILDLY fluctuate this winter, and your energy costs are going to vary wildly with seasonality if you're in many major markets. I pay close to $500 a month in electricity during the winter months, and I heat my home with natural gas. 85% of my fees are distribution fees and riders, and they increase in correlation with increased electricity use. I may be only using $30 more in electricity than I did before I started my tanks, but pay an extra $200 once fees are added in.

My gas bill reflects this same nonsense. This month's bill: $79.43. Total gas used? $12.58. Better yet: the average market price of Alberta natural gas for some of the last billing month was often BELOW zero cents. I just shake my head and pay the bills.

 

[Lbrdsoxfan]

See that first sentence has me frustrated because I feel like that’s the only answer you get to this question. (No offense) it’s a stupid answer, because how can any responsible adult just brush such a significant cost under the rug? A car guy doesn’t just go, we’ll if I’m worried about the cost of premium gas I guess I better not buy a car. They plan accordingly and buy a vehicle they can afford.

to your second point, that is exactly my question. With so many different variables, how can you even estimate something like heating costs. There has got to be a way to get at least a rough number based on how much water you have to heat versus the number of degrees above ambient temperature you need to heat it.

You can be frustrated all you want, but that's going to be the same answer from many of us. Reefing IMHO is treated like a hobby to me. If I'm interested in something, I do it. There is a limitation to the cost In willing to put in, but only I know my situation and I know my limitations (financial or otherwise). What I do know from a few decades of running my own tanks, whatever you estimate cost wise, it's usually higher than that and to be prepared for the situation as it arises.

End game is that if you want to do it, than do it. You have to chart out your own cost, we can't do that for you. I merely pointed out that electricity is the single biggest cost in MY situation, yours may be totally different.

 

[Kodski]

The best way to start your calculations may well be to negotiate a fixed term contract with your utilities. Variable rate contracts are going to WILDLY fluctuate this winter, and your energy costs are going to vary wildly with seasonality if you're in many major markets. I pay close to $500 a month in electricity during the winter months, and I heat my home with natural gas. 85% of my fees are distribution fees and riders, and they increase in correlation with increased electricity use. I may be only using $30 more in electricity than I did before I started my tanks, but pay an extra $200 once fees are added in.

My gas bill reflects this same nonsense. This month's bill: $79.43. Total gas used? $12.58. Better yet: the average market price of Alberta natural gas for some of the last billing month was often BELOW zero cents. I just shake my head and pay the bills.

Something I already do actually. It’s a little trick I learned from a professor. If you do a locked in contract, because energy prices almost always go up, you’ll actually be ahead for the term of the contract. Our bill is adjusted twice a year. Only once has it ever gone down. Luckily I live in the rural Midwest, so cost of living is low. Electricity and natural gas are somewhat cheap. At least when you compare the prices to larger populated areas.

 

[davidcalgary29]

You could probably get a useful number by contacting your municipal government to find out the cost of running the local indoor pool (and there must be a county or high school pool in your area, right?). And, okay, a large indoor pool is going to be 600 times the volume of your build, but you can divide those costs by the appropriate amount to look at heating (and possibly lighting) costs.

Edmonton now has saltwater swimming pools. I'd be curious to find out if that's a growing trend in the U.S., as it would obviously be a much better guide (although inexact) for home aquariums.

And I (and probably most of us) vastly overspend on fish foods. I could make perfectly healthy food by pureeing select finds in the seafood section at the local market and adding selcon and nori. I could certainly feed all my tanks on about a buck a day if I did this. I am promising myself right now that I will do this this winter.

 

[Kodski]

You can be frustrated all you want, but that's going to be the same answer from many of us. Reefing IMHO is treated like a hobby to me. If I'm interested in something, I do it. There is a limitation to the cost In willing to put in, but only I know my situation and I know my limitations (financial or otherwise). What I do know from a few decades of running my own tanks, whatever you estimate cost wise, it's usually higher than that and to be prepared for the situation as it arises.

End game is that if you want to do it, than do it. You have to chart out your own cost, we can't do that for you. I merely pointed out that electricity is the single biggest cost in MY situation, yours may be totally different.

Let me clarify, I in no way meant I was frustrated at you or was calling the response you took the time to type out stupid. I just think that for a hobby that can be so expensive, you’d think that we as hobbyist would have come up with a better way to calculate some of these expenses as opposed to saying just deal with it. Again, stressing that I totally understand a hobby costs what it costs, but there HAS to be a limit for everyone. 99% of us hobbyists are limited to our environment NOT our pocketbook. What I mean by that is typical we limit the size of our aquarium due to either our time or our house. When you’re only limited by your pocketbook, perspective completely changes. So my perspective isn’t, I can only fit a 200 gallon aquarium in my house so that’s as big as I can go, I’ll just deal with the running costs. My situation is, I can basically put in a 1500 gallon display tank, but I don’t know if I can actually afford to keep it running. If not, then what is the limit? Is it 500 gallons, 800 gallons? Hopefully that helps explain the situation I face and why I feel it’s important to actually spend the time to calculate out the costs involved and then ***** the situation.

manufacturing plants have very complicated processes but they don’t just say, we’ll I guess we will deal with the production costs and hope it doesn’t cost more than we will make. They do lots of costs analyzing, that is simply the quest I’ve set out on. I just don’t really know how to do something like that with so many variables.

 

[Epic Aquaculture]

My best recommendation is to ask others who have tanks the size that you are interested in, what their costs are, but also realize that electricity costs will vary depending on your location. For any large tank electricity is going to be the largest expense. My 500 gallon system costs me around $300/month to run, but I do get my consumables, other than electricity and water, at wholesale pricing as in addition to the 500 DT I run an aquaculture facility.

 

[Kodski]

You could probably get a useful number by contacting your municipal government and find out the cost of running the local indoor pool (and their must be a county or high school pool in your area, right?). And, okay, a large indoor pool is going to be 600 times the volume of your build, but you can divide those costs by the appropriate amount to look at heating (and possibly lighting) costs.

Hey that’s a really good idea! Thank you!

 

[Kodski]

My best recommendation is to ask others who have tanks the size that you are interested in what their costs are, but also realize that electricity costs will vary depending on your location. For any large tank electricity is going to be the largest expense. My 500 gallon system costs me around $300/month to run, but I do get my consumable other than electricity and water at wholesale pricing as in addition to the 500 DT I run an aquaculture facility.

Thank you for sharing. I may just have to do that. Seems like that may be the only way to get a halfway accurate assessment. Which if one was to spend enough time, you could break down electric costs via location and pipkin records then calculate using local kWh pricing.

 

[DaJMasta]

Heating shouldn't be too bad to calculate, you need to just calculate energy in and temperature desired over ambient. Your powerheads, lights, and filtration equipment will all contribute to this, probably hundreds of watts of heat in total on average over a day, but:
Raising 1g of water 1 degree C takes one Calorie of energy, which is 4184 Joules.
1L of saltwater is 1026g (specific gravity!), let's say you run your house at ~23C and want to run the tank at 26C - 3 degrees desired difference
1000 gallons is 3785 L, so: 3785 L * 1026 g * 4184 J * 3 C = 4.874*10^10
There's 3.6 million Joules of energy in a kwh, so divide by that = 13540kwh to get to the target temperature

Now that's not actually the number we want, because really we're looking at maintenance heat once it's arrived at that. For that, we need the surface area of the tank and the thermal conductivity of glass:
A 1000G tank is roughly 10x5x3, giving side panels of 10x3 and 5x3 feet. For the sake of simplicity, I'm going to omit the top and bottom panels (bottom is insulated, top is light canopy that can heat itself to ambient), but am going to double the surface area to include heat losses from the thinner sump and the water agitation/mixing that happens in the process. The water agitation of a reef tank also ensures relatively uniform temperature inside, which simplifies the calculation a lot. That's 90 square feet worth of side panels - 8.36 square meters, doubled to 16.72 m^2
As a randomly found figure for thermal conductivity of 3cm thick of glass being about 0.8Js*m*C

So you take your figures: daily energy required = Surface Area of the Tank * Seconds in a Day * Temperature differential all divided by the thickness of the glass divided by the thermal conductivity of glass
(16.72 m^2 * 86400 s * 3 C) / (0.03 m / 0.8 Js*m*C) = 115568640 J, or 32.10kwh per day.

Now I'd expect several hundred watts of added heat from water movement, so let's say 500W on average from pumps/skimmer/lights (a guess, no real idea), which is 12kwh of heat added to the tank every day from non-heater sources. Then you'd need an additional 20kwh per day from your heaters, so you're looking at a few dollars a day for just heating cost, depending on where you live and what your power price is. That also means you probably need a bare minimum of 1000W of heaters to accomplish this task - as 1000W of heating would be running, on average, an 83% duty cycle.

Now keep in mind that if you run your house much cooler, the temperature differential scales this number linearly. If you run an acrylic aquarium with better thermal insulation, or a thicker aquarium (also comes along with that), you lose less heat and will need less. If you an enclose the top (maybe with an automated vent for overheating) and enclose the sump area somewhat, you can reduce heat losses to the ambient and further reduce the amount required. It's also critical to figure that every watt added to your tank will also be heating your room, so in the summer you will be paying in AC cost to pull it out of your house, but in the winter you will not have to pay for it in heat from the furnace.


My numbers are guesstimates, but I think it shows that large tanks are not going to be massively expensive in terms of heating, especially if thermal/humidity control planning is built into the design of the installation. I think salt, RODI, lighting power consumption, additives, food, and replacement hardware will dwarf heater power consumption quite easily, to the point that I'd expect something like $20-40 a day to run a fully stocked tank of around a thousand gallons, not including livestock additions or new hardware additions.

 

[Kodski]

Heating shouldn't be too bad to calculate, you need to just calculate energy in and temperature desired over ambient. Your powerheads, lights, and filtration equipment will all contribute to this, probably hundreds of watts of heat in total on average over a day, but:
Raising 1g of water 1 degree C takes one Calorie of energy, which is 4184 Joules.
1L of saltwater is 1026g (specific gravity!), let's say you run your house at ~23C and want to run the tank at 26C - 3 degrees desired difference
1000 gallons is 3785 L, so: 3785 L * 1026 g * 4184 J * 3 C = 4.874*10^10
There's 3.6 million Joules of energy in a kwh, so divide by that = 13540kwh to get to the target temperature

Now that's not actually the number we want, because really we're looking at maintenance heat once it's arrived at that. For that, we need the surface area of the tank and the thermal conductivity of glass:
A 1000G tank is roughly 10x5x3, giving side panels of 10x3 and 5x3 feet. For the sake of simplicity, I'm going to omit the top and bottom panels (bottom is insulated, top is light canopy that can heat itself to ambient), but am going to double the surface area to include heat losses from the thinner sump and the water agitation/mixing that happens in the process. The water agitation of a reef tank also ensures relatively uniform temperature inside, which simplifies the calculation a lot. That's 90 square feet worth of side panels - 8.36 square meters, doubled to 16.72 m^2
As a randomly found figure for thermal conductivity of 3cm thick of glass being about 0.8Js*m*C

So you take your figures: daily energy required = Surface Area of the Tank * Seconds in a Day * Temperature differential all divided by the thickness of the glass divided by the thermal conductivity of glass
(16.72 m^2 * 86400 s * 3 C) / (0.03 m / 0.8 Js*m*C) = 115568640 J, or 32.10kwh per day.

Now I'd expect several hundred watts of added heat from water movement, so let's say 500W on average from pumps/skimmer/lights (a guess, no real idea), which is 12kwh of heat added to the tank every day from non-heater sources. Then you'd need an additional 20kwh per day from your heaters, so you're looking at a few dollars a day for just heating cost, depending on where you live and what your power price is. That also means you probably need a bare minimum of 1000W of heaters to accomplish this task - as 1000W of heating would be running, on average, an 83% duty cycle.

Now keep in mind that if you run your house much cooler, the temperature differential scales this number linearly. If you run an acrylic aquarium with better thermal insulation, or a thicker aquarium (also comes along with that), you lose less heat and will need less. If you an enclose the top (maybe with an automated vent for overheating) and enclose the sump area somewhat, you can reduce heat losses to the ambient and further reduce the amount required. It's also critical to figure that every watt added to your tank will also be heating your room, so in the summer you will be paying in AC cost to pull it out of your house, but in the winter you will not have to pay for it in heat from the furnace.


My numbers are guesstimates, but I think it shows that large tanks are not going to be massively expensive in terms of heating, especially if thermal/humidity control planning is built into the design of the installation. I think salt, RODI, lighting power consumption, additives, food, and replacement hardware will dwarf heater power consumption quite easily, to the point that I'd expect something like $20-40 a day to run a fully stocked tank of around a thousand gallons, not including livestock additions or new hardware additions.

This is exactly what I was hoping someone would have some experience in. Thank you very much! You just saved me weeks of learning thermal conductivity equations!

 

[DaJMasta]

This is exactly what I was hoping someone would have some experience in. Thank you very much! You just saved me weeks of learning thermal conductivity equations!

No problem, but to be clear, I neither have experience nor expertise with this. I just have a decent grasp of the concept, access to google, and tried to show my work in the event I overlooked something.

I'd like to emphasize the importance of designing for contingency and redundancy, though, as I have some familiarity with mission critical designs, and since such a large tank represents a gigantic investment of time and money. While I'm sure with some experience that you're aware of the potential risks and pitfalls, but regarding heat specifically:

I said 1000W of heaters for that theoretical situation would be the bare minimum, but I would never run less than 1500W in such a system - probably with 2000W or so being the target if that was your house temperature target. The amount of heaters also defines how quickly the tank can recover heat in the event of a drop, and defines how cold the tank gets if the ambient level drops. If your house heat goes out in the winter and the ambient temperature drops into the 50s, even 2000W of heaters will struggle to keep a liveable temperature in the reef (remember, that's only good for about 6C above ambient), but something like 3000W worth would actually give you enough heat to last at a cold temperature, and would probably shave a day or two off of the recovery time on the other side of the fault.

In the same vein, your lighting will likely be comparable power consumption to your heater bank, and to be most efficient, you absolutely want to be able to capture that heat in a hood and keep it against the water's surface (also reduces evaporative cooling). But if you're in the heat of summer and the AC fails, then you have that 1500W+ worth of heat generation stuck on the top of the tank, so I would also include at least two ventilation fans (redundancy, maybe even on separate control loops) in the canopy that automatically switch on when tank temperature starts to rise, and you want a single one of the fans to be able to dump most of the heat in the event they are needed.

Also worth mentioning - budget for potential increases in power cost. Europe is seeing record high electric prices right now, enough so that if the estimate for the tank in the US is $20-40 per day, it could easily be double that cost with current electric prices overseas, and the US is certainly not immune to those prices, especially if projected into the long term. I would add at least 50% extra to your upkeep estimate just to make sure you don't run afowl of near term inflation and price increases, and you probably want 100% extra budgeted for to be sure you don't have to take it down in the longer term.

While only peripherally related, I'd also like to emphasize the utility in keeping spares for main parts on hand, especially for things that aren't redundant. Much higher upfront cost, but being able to respond to a fault in a day instead of a week can make all the difference in the health of your animals when it's a mission critical part.

 

[killer2001]

If I was planning a large tank build I would probably consider solar panels.