Dealing with Hard Water in the Saltwater Tank

Perhaps you have heard the terms “hard” and “soft” thrown around in regard to aquarium water, but have you ever taken the time to learn what those terms mean? The hardness of aquarium water refers to the concentration of dissolved ions in the water, primarily calcium and magnesium – the more ions dissolved in the water, the “harder” the water will be. Though it is good to have some minerals in your tank water, it can become a problem for your fish if the water your saltwater tank becomes too hard. Fish cannot survive in water that has too high a concentration of heavy metals so you should take the time to familiarize yourself with some basic information about how to deal with hard water in the saltwater tank.

Causes of Hard Water

Many aquarium hobbyists are confused by water hardness but it is a very important aspect of water chemistry in the saltwater tank. Water hardness is closely related to aquarium pH and just as aquarium fish require a certain pH level in order to thrive, they also have preferences when it comes to water hardness. The hardness of aquarium water is affected by the mineral content. If you use tap water to fill your tank, the hardness of the water will be affected by the chemicals your city uses to treat the tap water. Even if you treat your tap water with an aquarium water conditioner to remove chlorine, other metals or minerals could be left behind. If you live in a rural area and use well water, it may have a naturally high concentration of limestone which could make it very hard.

How to Soften Tank Water

Hard water typically has a high pH and the minerals in hard water act as a buffer to keep the pH stable and alkaline – if you want to soften the water in your tank, you will also have to decrease the pH. In order to do so safely, however, you will need to buffer the water to a lower pH in order to prevent the pH from dropping so low that it has a negative impact on your water quality and on your aquarium fish. The key to softening the water in your tank is to do so slowly – you do not want to shock your fish with a drastic change in water chemistry and you don’t want to throw the pH balance off in the process either. One of the easiest ways to soften tank water is to dilute it with a source of naturally soft water such as rain or melted snow. Because you have a saltwater tank, however, you will need to first prepare the saltwater solution using this naturally soft water before adding it to your tank.

If this option is not available to you, you could try distilled water. The problem with distilled water – aside from the cost of purchasing large quantities of it – is that, in addition to having a very low mineral content, it is also devoid of oxygen. If you plan to use distilled water in your tank you will need to aerate the water first to increase the oxygen content. Another option is to simply install a reverse osmosis unit in your saltwater tank. This unit will demineralize the water that passes through it, thus saving you from having to purchase large quantities of distilled water. There are, of course, downsides associated with the use of reverse osmosis unit. Depending what size you need, the unit itself can be very expensive and some models have a very high rate of water consumption.

When it comes to dealing with hard water in the saltwater tank, you have several options to choose from. The best option, of course, is to find a way to work around the natural hardness of your aquarium water. Look for species of fish that are adapted to hard water or choose an alternative water source that is naturally soft.

References

“Aquarium Water Hardness.” Tropical Fish Success. < http://www.tropical-fish-success.com/aquarium-water-hardness.html>

Loiselle, Paul V. “Aquarium Water That is Too Hard.” FishChannel.com. <http://www.fishchannel.com/fish-health/freshwater-conditions/too-hard.aspx>

“Basic Water Chemistry Part 1: Water Hardness.” LiveAquaria.com. <http://www.liveaquaria.com/PIC/article.cfm?aid=60>

“Water Chemistry Basics: pH, Temperature, Water Hardness, Waste Breakdown, Minerals and Chemicals.” PetEducation.com. < http://www.peteducation.com/article.cfm?c=16+2154&aid=1526>