Thursday, September 23, 2021

The Right Sized Aquarium – Which Size is Right For You

November 29, 2008 by · Leave a Comment 

The old adage that says, bigger is better holds true for aquariums. Greater water volume is always better when it comes to keeping live fish in a glass box. Although, it is not impossible to successfully keep fish in a small space, there is a greater margin of error with a larger tank. One thing to consider when buying a larger tank is the cost of operating a larger filter and moving a larger amount of water volume.

Consider buying a ten-gallon freshwater aquarium. The tank itself may cost about 15 dollars US, the power filter 20 dollars US, the heater (if keeping tropical fish) 12 dollars US, ten pounds of sand/gravel 12 dollars US, water conditioner 10 dollars US, a net, cleaning sponge, and a lid adds another 15 dollars US. So for a ten-gallon tank, expect to pay about 80 dollars US without a light!

Compare that to a cost breakdown of a 50-gallon freshwater aquarium. The tank itself may cost about 70 dollars US, the filter about 70 dollars US, the heater 20 dollars US, 50 pounds of sand/gravel 40 dollars US, water conditioner 12 dollars US, net and cleaning sponge 8 dollars US, and it usually comes with a lid. So for a 50-gallon tank without a light, expect to pay 220 dollars US.

On the onset it looks more appealing to purchase the ten-gallon tank, but this is where most people make the mistake. With such a small volume of water, the temperature in a ten-gallon aquarium can fluctuate dramatically with the outside ambient temperature. This is very stressful for the fish. So what tends to happen is that people will buy the ten gallon tank, and save 140 dollars US, but then end up buying 140 dollars US worth of replacement fish. Or worse, frustration sets in and the tank ends up at the next garage sale.

A larger volume of water will help to stabilize the changes in temperature during summer months and water changes. Generally, if only 5-10 percent of water is changed in a 60-gallon tank every 2 weeks the fish tend to do well and parasites do not take over the tank. In contrast, with a small 10-gallon tank, a 5-10 percent water change could potentially devastate the chemistry of the tank. A small water change has the ability to alter the temperature more than 5 degrees Fahrenheit which will stress the fish and cause disease. Once the fish contract disease it is also easier to treat in a larger tank.

Medicating the fish in a 50-gallon tank will allow for a less precise dosing of medication. When treating fish in a small tank the amount of chemicals being added needs to be measured carefully and double-checked before being poured into the tank. A miscalculation could reveal deadly results. In contrast, that same miscalculation could go unnoticed in a larger tank. That is not to say that medication does not need to be measured when being added to a large tank. It is easier to treat fish in a tank with more water, but if the guidelines are followed, the fish has the potential to recover no matter which sized tank they are in.

In a large tank, obviously large fish can be kept where they have adequate room to swim and grow. A large fish can be kept in a small tank, but the fish will grow to the size of the tank. If the tank is smaller than the maximum size of the fish, the fish will grow up deformed with internal organ dysfunctions.

Needless to say, it is much better for the fish to pair appropriately sized fish with appropriately sized homes. People should not keep German shepherds in crates suited for Yorkshire terriers, and in the same way Oscars should not be kept in 10-gallon fish tanks! An appropriate sized tank for a full-grown Oscar would be 36in x 18in x 16in. In a tank this size the fish has the ability to turn around comfortably. The adage that 1 gallon of tank water is required for 1 inch of fish does not hold true.

The fish keeper must consider the total mass of the fish. Ten inches of neon tetras does not equate to a 10-inch Oscar because the girth of the Oscar is much larger than the tetras. Thus, when deciding which tank to choose, research the maximum size of the fish you wish to keep and buy a tank where the fish can turn around comfortably.

If considering buying small community tank fish such as guppies, mollies, platties, and small gouramies check out the biUbe at

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