How Much Does it Cost to Maintain a Saltwater Aquarium?

Saltwater aquariums can run the gamut from simple, 50 gallon tanks with ac pumps, all the way to thousand gallon systems with hundreds of fish and coral, hard plumbing, sumps, electronic controllers, app-enabled lighting, and even full on computer control with automatic water changes. 

Regardless of which system you have, or plan to build, the formula for calculating how much maintenance will cost you is the same. The only difference is the cost of each variable or component.

The Components of Saltwater Aquarium Maintenance

Aquarium maintenance occurs on a daily, weekly, and monthly basis. The associated costs build with each action. Calculating how much it will cost to maintain your aquarium is simply a matter of adding together the components for your system. 

The components of saltwater aquarium maintenance are: 

• Water

• Salt 

• Additives

• Buffers

• Filter media 

• Water analysis 

• Food

• New Livestock

  
  

The Maintenance Cost of Water

For any aquarium, water is the base on which other components are added. You should never use tap water with saltwater aquariums as it contains many components already. When you add your buffers and additives to tap water, it reacts in an unpredictable way and creates a mystery mixture that does not belong in the scientifically detailed ecosystem of a saltwater aquarium. 

You should always use Reverse Osmosis De-Ionized (RODI) water to add salt mix to. 

The question then becomes whether you produce RODI water at home, or purchase from a store. Producing RODI water at home, then mixing your salt into it, has a higher upfront cost, but will definitely pay for itself in the long run. See this article on the cost and methodology for building a saltwater mixing and water change station with RODI water. 

RODI Water at Home

Even though your tap water is not suitable for aquarium use, you can install an RODI filter in your home and make your own reverse osmosis deionized water. This article gives a quick introduction to RODI filters. Once you’ve installed a filter, you can start making your own pure water for as little as $.15 per gallon. 

Salt Mix

Salt mixes are manufactured in a variety of ways and are formulated for different types of saltwater aquariums. The cost of salt mix for a fish only saltwater aquarium will be less than a full reef aquarium as it lacks the elements added specifically for coral health. 

Cheaper salt mixes have more impurities which results in build up in your mixing bin and in your aquarium. I don’t recommend using anything less than pharmaceutical grade salt mixes, or at the very least, mixes where the salt was mined from the ground, but has been properly filtered. 

Ideally, choose a brand that has the ICP-OES batch test results printed on the box. 

With all this in mind, a low end salt is $0.46 per gallon and a high end salt is $0.67 per gallon, equaling an average of $0.56 per gallon. If you perform a 20% water change every week, that's $.112/gallon/week. 

Pre-Mixed Saltwater From the Store. 

If your aquarium is small enough and installing your own RODI filter is more than you need, most aquarium stores will sell pre-mixed saltwater. At retail, pre-mixed saltwater will cost you at least $1.00 a gallon. 

Invest in Your Salt Mix Setup

All things considered, the most cost effective version of saltwater for your aquarium is to install a mixing vat and water change station at home. 

The up front cost of the saltwater mixing and water change station is about $1,500 for a 100 gallon vat. 

The cost of RODI and salt mix is about $0.71 per gallon at home

The cost of pre-mixed salt water is $1.00 at the store. 

$1.00 - $.71 = $.29 savings 

$1,500 / $.29 / gallon = 5,172 gallons of water mixed before the mixing station pays for itself. 

For a 100 gallon aquarium, at 25 gallon water changes a week, that's 206 water changes or 3.9 years before the mixing vat pays for itself in savings from not having to buy water from the store. If you plan on having your aquarium for longer than 3.9 years, it makes financial sense. 

Additives and Buffers

Additives and buffers are chemicals that get added to water in order to change its chemistry. The most common additives in saltwater aquariums are: 

• Sodium carbonate (to raise alkalinity) $0.00147 / gallon / week

  • $0.001/mL 0.21mL/gallon) = $0.00021 / gallon 7 days = 0.00147/gallon/week 

    • 0.21mL/gallon is the average daily consumption of sodium carbonate in a medium load reef tank. To get more specific with the cost, increase or decrease the 0.21 mL/gallon depending on your rate of consumption. 

• Calcium chloride (to raise calcium) $0.00147 / gallon / week

  • The rate of calcium consumption can vary. It may be equal to, higher than, or lower than carbonate consumption. For that reason, I’ll use the same formula as the sodium carbonate above. 

• Magnesium sulfate or chloride (to raise magnesium) $0.00147 / gallon / week

  • Magnesium consumption is generally lower than carbonate or calcium. However, the amount of buffer per gallon is higher to achieve a similar increase in concentration. Because the amount varies so widely, I’ll use the same formula as sodium carbonate and calcium chloride above to estimate an average amount. 

• Trace elements $0.011/gallon/week

  • $0.023/mL 0.25 mL/gallon = $0.0057/gallon 2 = $0.011/gallon/week. 

    • The average cost of a trace element product for a full reef tank is $0.023/mL. Multiply that amount by the recommended dosage amount of 0.25 mL/gallon, then multiply by the recommended dosage frequency of twice a week and you get $0.11/gallon/week. 

• Coral supplements (amino acids) $0.0119/gallon/week

  • $0.085/mL 0.02 mL/gallon = $0.0017/gallon 7 = $0.0119/gallon/week

    • The average cost of a coral amino product for a full reef tank is $0.085/mL. Multiply that amount by the recommended dosage amount of 0.02 mL/gallon, then multiply by the recommended dosage frequency of 7 days a week and you get $0.0119/gallon/week. 

• Nutrient supplements (nitrate and phosphate increasers) $0.021/gallon/week to raise nitrates by 5 mL

  • $0.015/mL / 25 gallons = $0.0006/ml/gallon 5 mL = $0.003/gallon 7 days = $0.021/gallon/week

    • 5 mL would be an average dose to raise the nitrate level in a 25 gallon aquarium by 5 ppm. If you want to get even more specific with the cost, change 5 mL to the PPM of nitrate you are trying to raise your tank by. 

• Medication and Dips (used when acclimating) $0.07/mL

  • $0.075/mL 20 mL = $1.51/usage 2 uses per month = $3.02 / week. 

    • The average cost of coral dip is $0.075/mL. Multiply that by 20 mL to create a dip solution for any size aquarium. Then multiply that by the average number of times a month you’ll be creating a solution to dip new corals and you get the weekly cost. 

      • If you buy corals every week, the uses per month increases to 4. If you make a 2 gallon mix when you dip, then use 40 mL in the formula instead of 20 mL.

        
        

Filter Media

Filter media is an expense that varies widely for every aquarium. Some “natural” style systems don’t use physical or chemical media at all. While others rely heavily on fleece roller pads and reactors full of resins. 

Filter media can quickly become an expensive part of your maintenance if you have to keep replacing physical media every few days and swapping out chemical media every few weeks. 

Physical Media

Depending on your bioload, filtration media will need to be replaced on a regular schedule. This article details how often to clean an aquarium. Depending on the filter type, tank size, and bioload, new socks, pads, or sponges for physical filtration can cost as much as $0.04/gallon/week or as little as $0.02. The average per gallon is $0.03.

Chemical Media

Activated carbon and ammonia, phosphate, and nitrate adsorbers are forms of chemical filtration. As they adsorb their respective nutrients and chemicals they will need to be replaced. 

Depending on the bioload of your tank, expect to spend, on average, $0.04/gallon for carbon and between $0.20 and $0.07/gallon for nutrient adsorbers, with $0.13 being the average. 

Professionally, I don’t use carbon in saltwater tanks as I believe it pulls too much from the water column. I generally only use chemical adsorbers if they are needed to address a specific problem, like heavy metals in the water or high phosphates. 

Protein Skimmer

Protein skimmers are considered chemical filtration, but have no recurring cost other than electricity and replacement parts as needed. The upfront cost can be found in this guide on the cost of saltwater Aquarium. 

Biological Media

The main type of biological filter media is a habitat in which beneficial bacteria live and reproduce. This media type should never be replaced and therefore has no maintenance cost. 

Biological media can also include periodically adding live bacteria, the cost of these supplements is about $0.035/gallon/week. 

• $0.035/mL 1 mL/gallon 1 dose per week = $0.24/gallon/week

  • The average cost of probiotic bacteria is $0.035/mL, multiplied by the dosage per gallon of 1 mL, multiplied by the dosage frequency of once per week is $0.035/gallon/week. 

BioPellet Reactor

There are several ways to add carbon to your tank for microbiome health. The first is by adding a liquid carbon supplement. This will cost about $0.0056 per gallon / week.  

• $0.04/mL $0.02 mL/gallon = $0.0008/gallon 7 days = $0.0056/gallon/week

  
  

  • The cost of an average liquid carbon supplement for bacteria is $0.04/mL; multiply that by the recommended dosage per gallon for an average reef tank, then multiply that by the recommended dosage frequency of 7 days a week and you get $0.0056/gallon/week. 

Liquid carbon supplements can be expensive, an even more cost effective and efficient form of carbon injection is using a bio-pellet reactor. The maintenance cost of a reactor is the price of the media it uses, called bio-pellets. These pellets cost about $0.0033/gallon/week and can last for 6 months before needing to add more. The reactor should always hold about 1 cup per 50 gallons of system volume. Top off your reactor to maintain this volume. 

• $0.08/gallon / 24 weeks = $0.0033/gallon/week. 

  • The average cost of bio-pellets is $0.08/gallon, divided by 24 weeks in 6 months = $0.0033/gallon/week. 

Calcium Reactor

Calcium reactors are used to infuse calcium and carbonates (alkalinity) into a high demand aquarium with a heavy coral bioload. These reactors are phenomenal at maintaining calcium and carbonates when there are high rates of extraction. 

The maintenance cost of a calcium reactor includes the media used in the reactor at about $0.021/gallon/week and the cost of the CO2 at about $0.00062/gallon/week.  

The reactor media may only need to be replaced every 1 to 3 months depending on demand, while the CO2 should last 2 to 6 months. 

• $0.175/gallon / 8 = $0.021/gallon/week 

  • The average cost of calcium reactor media is $0.175/gallon, divided by 8 weeks in 2 months = $0.021/gallon/week.  

    
    

• $0.01/gallon / 16 = $0.00062/gallon/week.

  • The average cost of CO2 gas is $0.01/gallon, divided by 16 weeks in 4 months = $0.00062/gallon/week. 

Controllers

Aquarium controllers can have a substantial up front cost, but usually don’t occur ongoing maintenance costs. The exception is if you have an automatic water analyzer attached to your controller, in which you will need to periodically purchase reagents. 

Water Analysis

At Home

If you're testing at home, using color changing liquid reagents, handheld colorimeters, or titration tests, you can expect to spend around $.10 per test. With around 6 tests per week, that is $.60 per week in testing. 

At The Store

Most pet stores will not charge for water analysis if you're a regular customer. I have seen some stores charge up to $2.00 per test when using higher grade testing equipment. 

Food

For most saltwater aquariums, feeding dry and frozen food every day, costs about $0.050/gallon/week. If your aquarium is heavily stocked, or if you're feeding large fish with specialty diets, expect to spend closer to $0.07/gallon/week 

New Livestock

While I don’t consider this maintenance per say, a recurring cost for most saltwater aquariums is new livestock. This amount is relative and could be as little as a few hundred dollars a year for established aquariums or up to hundreds of dollars a month for new aquariums. I won’t include this in the final calculation, but consider how much adding livestock will cost you. 

So How Much is The Cost of Maintaining a Saltwater Aquarium?

Adding all our average costs together, the final total to maintain an average saltwater aquarium is about $ 1.00 per gallon per week, plus $3.62 per week for testing. However, there are a lot of redundancies in the table below. 

You don’t need to include store pre-mixed and home-mixed saltwater if you're only using one of them. Other redundancies include bio-pellets and liquid carbon supplement, and calcium buffer and calcium reactor media. 

With this in mind, the actual average cost of maintaining a saltwater aquarium is closer to $0.47/gallon/week. 

When doing your own calculations, each total is per gallon/week. However, if you do water changes biweekly, then your total will be different. For example, the average cost of salt mix per gallon per week of $0.112 would be $0.056/gallon/week if you did water changes every two weeks. 

Finally, when doing your own calculations, remember, the $0.60 per week for water testing and $3.02 per week for coral dips is not per gallon, it's per week. Add the $3.62 to the end of the weekly total for your system volume, not the per gallon total. 

Keep in mind these are averages. Some people buy in bulk, do less frequent water changes, or only feed dry food. These can change your weekly maintenance total significantly. 

Component	Per gallon / week ($)	Per Week ($)
RODI (home)	​.15
RODI (store)	​.50
Pre-Mixed (store)	.2
Salt Mix	​.112
Sodium carbonate (to raise alkalinity)	.00147
Calcium chloride (to raise calcium)	.00147
Magnesium sulfate or chloride (to raise magnesium)	​.00147
Trace Elements	.01
Coral supplements (amino acids)	.0119
Nutrient supplements (nitrate and phosphate increasers)	.021
Medication/Dip		​3.02
Physical Filter Media	​.03
Nutrient adsorbers	​.13
Live Bacteria	​.035
Liquid Carbon Bacteria Supplement	.0056
Bio-Pellets	.0033
CO2 Gas	.00062
Calcium Media	.021
Water Test		.6
Food Light Bioload	.05
Food Heavy Bioload	.07
TOTAL	.47	3.62

I hope this article helps you calculate the cost of maintenance for your saltwater aquarium, and gives you an idea of what to expect when building your next system. 

As always, If you need any help or have any questions about the cost of maintaining a saltwater aquarium don’t hesitate to contact us and we’ll figure it out together.