As the old saying goes, “Take care of your water and your water will take care of your fish.” I heard this saying many decades ago, and this saying is very much as true today as it was when I was a little kid eagerly purchasing my first goldfish in a shop in Cartimar.

Yes, successful fishkeeping is all about your tank water. Keep your tank water keyed to the needs and liking of your fish, then you should be on your way to a successful fishkeeping hobby. This is true because water is everything to a fish. Thus the water in your aquarium must be the perfect environment for your fish.

To have this perfect environment, you will have to look at two things about your tank water: water parameters and water quality. These are two different things that have significant effects on the health and well-being of your fish. This column therefore aims to explain the difference between the two and discuss why knowing about water parameters and water quality is important to fishkeeping.

Water Parameters

I define “water parameters” as the chemical make-up of your tank water. In some sense, the fishkeeper needs to know what water characteristic is best for the fish he or she is keeping.

Grade school science has taught us that water is two parts hydrogen and one part oxygen or H2O. Yes, this is true as this is the molecular structure of pure water. However, water as we experience it in nature is not just an aggregate of water molecules, but a mixture consisting of H2O and “a lot of other stuff.”

This is due to the ability of water to dissolve a variety of different substances, which is why it is such a good solvent. Water is considered the universal solvent, and water in nature has a lot of dissolved substances in it that dictate its characteristics. The environment where water is found dictates its chemical make-up. Therefore, water collected from different places has different water parameters.


This explains why South American Cichlids from the Amazon River have a totally different water parameter requirement compared to what a Cichlid from the Rift Valley Lakes of East Africa needs. The Amazon River runs through the greatest rainforest in the world. What with all the leaves, trunks, and branches soaked in the river, these turn the water acidic. Thus Cichlids from the Amazon River, like those found from the genus Apistogramma, Crenicichla, Pterophyllum, Heros, Geophagus, etc., must be given a tank with soft and acidic water.

On the other side of the earth, Cichlids from form the Rift Valley Lakes of East Africa live in ancient lakes surrounded by limestone. Thus, water parameters in Lake Malawi, Lake Tanganyika, and Lake Victoria are hard and alkaline. Therefore, keeping Cichlids from the genus Altolamprologus, Neolamprologus, Tropheus, Haplochromis, and Aulonocara, among others, will require very hard and alkaline water.

The subject of water parameters is very broad and there are many substances, trace elements, and other factors that may affect it. But the most important concerns for the freshwater fishkeeper are pH and hardness. These two factors have significant effects on your fish if these are not monitored and proper values provided for.

What is pH? The term “pH” is commonly heard in conversations among fishkeepers. However, not everyone is able to comprehend concept behind pH, and even fewer understand the importance of maintaining stable pH levels in their tanks.

In the term “pH,” the “p” stands for “potential” and the “H” stands for “hydrogen.” pH is thereby the “Potential of Hydrogen.” This is the quantity of hydrogen or hydroxyl ions in water that determine whether the solution is acid or alkaline.

In measuring the acidity or alkalinity of water, we use the pH scale. The pH scale ranges from 0.0 to 14.0, with 7.0 being neutral or the point at which water is neither acidic nor alkaline. As the scale goes down, the water becomes more acidic, and inversely, as the pH goes up, the water gets more alkaline.

Since fish come from different waters with different pH readings, it is best to know what is the pH of the water the fish you are keeping comes from. In the Philippine fishkeeping scene, we are very lucky that about 80% of aquarium fish can do well in a pH range of 6.5 to 7.5. In most parts of the country, this range is very much attainable through a local water distributor. You may therefore assume that the average Filipino fishkeeper should have an easy time attaining the ideal pH for most of his or her fish. It may also be assumed that 20% of aquarium fishes available will require lower pH or higher pH levels in the water than usual. These should be the more challenging ones to care for.

One very important thing to know about the pH scale is that it is logarithmic. For each difference between two whole numbers, it is ten times more acidic or ten times more alkaline. To clarify, from a neutral pH of 7.0, the reading pH 6.0 is ten times more acidic than pH 7.0. Further on, a reading of pH 5.0 is a hundred times (10 x 10) more acidic than pH 7.0. Inversely, a pH of 8.0 is ten times more alkaline than pH 7.0. Likewise, a pH of 9.0 is a hundred times more alkaline than pH 7.0.

Bearing this in mind, it is very important that the pH of your water be stable and only fluctuate by 0.3 to 0.5 points, as anything more may be stressful and hazardous to your fish.

What is water hardness? The second aspect of water parameters is water hardness. Simply put, water hardness is the measure of dissolved mineral salts in the water. As explained earlier, water in nature does not exist in its pure form of H2O. Depending on the source, water is a mixture of H2O and mineral salts.

There are two basic types of hardness that are of importance to fishkeepers: general hardness (GH) and carbonate hardness (KH). The combined GH and KH is sometimes termed Total Hardness, but this is of less importance because the GH and KH individually impact the water in different ways.

General hardness is basically determined by the minerals calcium and magnesium. GH is measured in several different ways. The most popular methods used in the fishkeeping hobby are parts per million (ppm) and degrees (dH or dGH). One dGH equals 10 milligrams of calcium or magnesium oxide per liter which is likewise equivalent to 17.848 ppm. Multiplying dGH by 17.9 gives ppm, and inversely dividing ppm by 17.9 gives dGH.

General hardness is very important to learn because each fish has its own GH requirements. Some fish like the Altum Angelfish (Pterophyllum altum) requires very soft to soft water. On the extreme end, the Blue Zaire Frontosa (Cyphotilapia gibberosa) requires hard to very hard water. If these GH requirements are not given, then the fish will only be stressed and will most likely die. Also, since their GH requirements are on the extreme ends of the chart, it is impossible to have both species in one tank.

On a side note, GH is also referred to as “permanent hardness” because it cannot be removed from water by boiling.


This appeared in Animal Scene magazine’s August 2017 issue.