How to Adjust a Fish Tank’s Volume

Knowledge of how much water your aquarium holds can be crucial when preparing to move or managing tank maintenance costs. Our calculator estimates your aquarium’s water volume capacity based on your measurements.

This calculator is specifically tailored for rectangular tanks but works just as efficiently when applied to cylinder variations and bow fronts. Simply input your tank’s length, width and height.


An aquarium substrate layer can be an invaluable addition to any tank, providing additional insulation and keeping water nutrients at optimal levels while encouraging beneficial bacteria to flourish in filtration processes. Furthermore, substrate provides plant roots a home to settle in; without it they would flounder around aimlessly without being able to secure roots into the bottom, which is key for planted tanks.

Substrates for aquariums vary based on personal taste and what kind of fish are living in them, however, there are some general guidelines to keep in mind. A common recommendation is one pound per gallon of tank volume – although this can be confusing because most people base this number off what their tank’s label says (ie 10 gallon), rather than its actual internal water volume.

Aquarium substrates come in all sorts of shapes, colors and compositions – from inert substrates like sand and gravel, to active ones that affect water chemistry directly like crushed coral, soil or peat moss. Particle size also impacts your aquarium water chemistry: larger particle sizes allow uneaten food and waste from fish to slip through unnoticed, increasing ammonia and nitrite levels while fine-grained substrates may compact over time, blocking oxygen flow leading to anaerobic pockets of hydrogen sulfide gas that poses risk for fish.

Calculating aquarium substrate requires knowing how much room your tank will occupy after adding substrate and subtracting that from its actual internal volume. This approach is accurate even for non-rectangular tanks; you’ll just have to use different calculations. In such instances, measure height and width before converting inches to gallons using formula (l x w x d)/231.

Substrates can be invaluable tools in aquariums with planted tanks, serving to increase overall nutrient levels while adding insulation and supporting bacterial growth to optimize filtration. Furthermore, substrate can act as a foundation for plant roots to settle into while adding visual appeal and making your aquarium truly stunning.


Filters in fish tanks help ensure water remains flowing, preventing stagnant areas and limiting oxygen inhalation. However, if too much oxygen enters at once and too strong a current develops in your tank, too strong currents could damage or trap fish inside its filters and injure them.

Adjust the flow rate of your aquarium filter according to its specific needs, but also take into account what kind of filtration your fish and aquarium plants require for survival. Some species require high water flow while others can get by with lesser volumes.

Most fish tank owners opt for an outside filter attached to the back of their aquarium. But there are also internal filters known as power filters that sit within your aquarium itself and work by sucking water up through a supply tube from your aquarium, sending it through numerous compartments with various forms of filtration media and back through an overflow. There’s an array of sizes available to meet every fish tank owner’s need – beginners or veteran aquascapers alike can maintain these simple yet powerful devices easily!

Canister filters are another type of fish tank filter. These work by sucking water from an aquarium through a supply tube and expelling it through an outlet at the top of the filter. Canister filters are highly versatile, as they come in various sizes to fit both freshwater and saltwater aquariums; moreover, their durability makes them an excellent option for larger tanks.

While canister or power filters may suffice for most fish tanks, aquascapers sometimes prefer the more natural look of an internal aquarium filter. These types of filters come in various sizes to meet the needs of different tanks; large or deep aquariums especially benefit from having one installed.

Remember when calculating the volume of a fish tank that substrate and decorations can consume a great deal of space. To get an accurate measurement, subtract the height of your substrate layer from your estimated aquarium water volume; if your tank has non-rectangular sides you should also factor them in.


The overflow is the system through which water from your display tank is taken to either a sump or filtration system, typically comprising of an overflow box, tubing, and pump. It serves both to control water level in your tank as well as act as a safety net should any piece of equipment fail (like power outages or siphon failure).

There are various types of overflows you can use. An internal hang-on overflow is usually the least costly and easiest to install; however, they’re more prone to failure, since tubes break or pumps fail more easily than slim external overflows that take up less space in an aquarium’s sump. Slim external overflows offer far fewer failure points while taking up far less space – however their only drawback may be noise due to constant water movement nearing their drain box drain.

Internal built-in overflows come in various sizes. These can often be found on Reef Ready tanks such as Red Sea Reefer or Durso systems and tend to be more costly than external or hanging on overflows; however, they save the hassle of drilling your tank! Unfortunately these overflows are loud; their water flows through perforated holes similar to waterfalls producing noise similar to the waterfall itself.

If you want to solve these issues, one way is to switch out the perforated tube for a plain pipe or cut a slot into your overflow tower to create a more open system and allow water to fall more slowly without making sucking noises. For this to work properly though, make sure that any holes you cut aren’t too small; otherwise it may cause too much water to flow back into the tank too quickly and forcefully; if this occurs it indicates that this hole needs expanding.

Water Changes

If you own a fish tank, regular water changes are key to maintaining optimal conditions. Water changes help remove waste products that accumulate in the substrate as well as maintain an effective balance of beneficial bacteria in your tank’s ecosystem.

As a rule of thumb, it’s a good idea to calculate how many gallons are in a tank and change 10% of the water in your tank each week. This can easily be accomplished by siphoning out old water into a bucket and replacing it with fresh, treated water. While you might be tempted to use something like a jug or pump instead, doing this could cause even more strain by uprooting aquatic plants and disturbing substrate.

At any water change, it is crucial to add the new water slowly so as not to shock its inhabitants or cause spillage or overflow. Furthermore, use only tap water with similar temperature as that found within your fish tank – anything too hot or too cold could stress out fish while killing coral and live rock in its wake.

Use of a small tube when siphoning out tank’s water can make this task simpler and more accurate, and battery operated siphons are ideal. Traditional siphons cannot offer such control of flow rate as battery powered siphons do – plus battery powered allows you to ensure only dirty water is removed while also sucking up any physical waste particles on substrate which can come up during heavy stocking aquarium setup.

When updating the water in your fish tank, be sure to fill your bucket with the exact temperature as that of the tank. Many people believe that tank size alone determines stocking levels – but in reality experiments have demonstrated that its quality rather than volume hinders fish growth.