Practical Water Chemistry by Shelli Wittig
Water chemistry can be a bit daunting to
the beginner aquarist; at least it was for me. When I got started in the hobby
I was sold a complete test laboratory which included tests for 5 different
things. I was diligent about testing and recording the results, but never had a
very good understanding about what these properties were and how they affected
my fish. This made it very difficult to actually use any of the data I was
As it turns out, it’s not really all that
complicated. Fish keepers are mainly concerned with how acidic or alkaline the
water is, and what concentration and variety of dissolved minerals it contains.
These are expressed by measuring three basic properties: pH, GH and KH.
pH is probably the single most important
property to understand and monitor. It refers to water being acidic, basic
(alkaline) or neutral. With a measurement of 7 being neutral, less than 7 is
acidic and greater than 7 is alkaline. While common tropical fish are happiest
right around neutral, African cichlids prefer the following alkaline ranges:
Lake Malawi species: 7.4 - 8.6
Tanganyika species: 7.8 - 9.0
Lake Victoria species: 7.2 - 8.6
Fish are extremely sensitive to changes in
pH and it is important to maintain a stable level in your aquarium. When
adjustment is necessary, avoid changes greater than .3 units per day. Keep in
mind that the pH scale is logarithmic (like the Richter scale used to measure
the intensity of earthquakes). This means, for example, that a pH of 8.0 is 10
times more alkaline than a pH of 7.0.
General hardness or total hardness is a
measure of the magnesium and calcium in the water. Africans are most likely to
appear vibrant and colorful in aquariums with a general hardness ranging from
160-320 ppm (ppm) or 9-18 dH (Deutsch hardness). Because dH values refer to a
German hardness scale, I have heard GH mistakenly referred to as German
hardness which is incorrect. This is a mix-up between the particular water
property being measured and the scale on which the result is expressed. There
is also a Clark scale, but since I am not personally familiar with it and don’t
know how widely it is used I chose not to calculate the target range using that
scale. Examine your test kit carefully so that you are certain what scale it
uses. The following conversion table may be helpful: 1 dH = .65 Clark = 17.9
It should be noted that GH levels naturally
drop over time because minerals do not stay suspended in water very long. This
is one of many good reasons for regular partial water changes.
KH or carbonate hardness, also known as
buffering capacity or total alkalinity, is a measurement of carbonates and
bicarbonates in the water. It is best described as water’s ability to keep the
pH stable as acids or bases are added almost acting like a sponge for those
additives so they cannot affect the pH. Without adequate buffering, the pH in
your aquarium will eventually drop because the end result of the nitrogen cycle
is nitrate (nitric acid), which slowly builds up between water changes. With
sufficient buffering the pH remains stable. For a Rift Lake aquarium, KH is
ideally in the range of 180-240 ppm, or 10-14 DH.
Do I really want to tamper with these
properties? Some people are diligent about testing and taking calculated steps
to achieve specific targets, while others defiantly reject that approach and
claim to have a thriving aquarium without complication or added expense. I believe
that success with the latter would not be without a fair degree of luck. Some
hobbyists are fortunate to have hard water with a high pH right out of the tap
and still others have selected species that are more adaptable than others to
With a little experimentation and
application of the basic knowledge derived here, you can take a more proactive
approach and perhaps even find that the challenge of creating the perfect water
chemistry makes aquarium maintenance more fun. You will be rewarded with
healthy, colorful fish that flash their fins, exhibit natural behavior and even
spawn. More importantly, you are much less likely to have to deal with
unexplained illness or death.
How do I make changes? To raise KH and pH,
add baking soda (sodium bicarbonate). A baseline recommendation is 1 teaspoon
per 5 gallons of water (dissolve in a cup of aquarium water if adding directly
to the tank). For an established aquarium, remember to take this slowly as fish
are highly sensitive to pH changes. Incidentally, there are off-the-shelf
products available for this purpose, but baking soda is cheaper and most people
already have it on hand. Wardley’s product Raise pH® is sodium bicarbonate, whereas
Aquarium Pharmaceuticals pH Up® is sodium hydroxide.
Instead of relying solely on additives for
buffering, you can use crushed coral, crushed oyster shell, crushed limestone,
aragonite or dolomite as a substrate. Seashells, limestone rock or Texas Holey
Rock (also limestone) will all help to provide continuous buffering as they
leach carbonates into the water.
Driftwood (use only safe and sterile pieces
intended for introduction into an aquarium) will leach tannic acid and
consequently lower pH. It can discolor the water as well, and is typically not
recommended for Rift Lake aquariums. Sodium biphosphate reduces pH, and pH
Down® by Aquarium Pharmaceuticals contains sulfuric acid to accomplish the
task. I consider intentionally lowering pH a tricky and dangerous business
because it is impossible to do without affecting KH. You must first use up the
buffering capacity and then any further steps you take will immediately lower
the pH. The danger is that with no buffering capacity remaining, your resulting
lower pH is extremely susceptible to fluctuation. Luckily, African cichlids
like a high pH and most of us need never take any steps to lower it.
To raise GH, add Epsom salt (magnesium
sulfate). A baseline recommendation is 1 tablespoon per 5 gallons of water
(dissolve in a cup of aquarium water if adding directly to the tank). While
adjusting total hardness is not as potentially dangerous to your fish as
adjusting pH, dramatic changes of any sort can be stressful. Flashing (rubbing
on the gravel or rocks) is often attributed to changes in hardness. Personally,
I would make any substantial GH adjustment over a period of 2 to 3 days if my
aquarium were already stocked with fish.
Rockwork in your aquarium helps with
hardness too. While the effects are negligible (except with limestone, which is
mostly calcium carbonate and therefore works on GH and KH), total hardness is
likely to be higher with rocks in the tank than it would be without. Limestone,
Texas Holey Rock (also limestone), pagoda, tufa, lace, petrified wood, quartz,
slate, marble, and even common river rock can all be used in your aquarium safely.
Be sure to thoroughly clean and sterilize (boil) anything suspect before
putting it in your tank.
Hard water can be softened by diluting it
with distilled water, but it is rarely necessary to lower GH for an African
cichlid aquarium. While researching for this article I spoke with an individual
whose water comes from a well and is extremely hard. He dilutes it with both
R/O water (reverse osmosis) and water run through a home water softener, just
to bring the total hardness down to 40 dH. Apparently his cichlids (both
Malawians and Tanganyika’s) are unable to read the test strips because they are
doing just fine in both of his aquariums!
Where do I start? The best place to start
is with your tap water. Test it, experiment with Epsom salt and baking soda,
retest, and determine what ratios are needed to properly condition the water
you will add during scheduled water changes. Test your tank water between
changes to be sure your measures are sufficient.
NOTE: To test your tap water for pH,
de-chlorinate a sample and then circulate/aerate it for at least 60 minutes
before testing (overnight would be even better). This will allow any gases to
escape that could temporarily lower pH and skew your test results.
Is there anything else I need to add? Aside
from products to treat your tap water for toxins (see "Water
Treatment") you can provide a fine environment for your African cichlids
simply by using Epsom salt and baking soda to obtain pH, GH and KH in the
ranges suggested here. Still, some people like to take it a step further and
use additives to provide other trace elements found in the Rift Lakes. They
believe that creating conditions as natural as possible will result in
extraordinarily healthy and colorful fish. Other folks feel that since most of these
fish are bred and raised in aquariums, they would not miss the precise
chemistry of lake water they have never even been exposed to.
Since beginners are likely to be
overwhelmed with the various opinions and products available, here are a few
basic options for working with your water chemistry, listed from most
economical to least.
Create your own "Rift Lake
Buffer/Cichlid Salt" with Epsom salt, baking soda, and salt. You can use
aquarium salt or table salt (baseline recommendation is 1 tsp per 5 gallons of
water). They are the same thing, sodium chloride(NaCl) except that table salt
often contains iodine and anti-caking agents. There are some people that warn
against the additives in table salt, but just as many people claim to use it
successfully. If this concerns you buy aquarium salt. Sodium and chloride are
both found in the Rift Lakes, and salt contributes to the fishes protective
Use Epsom salt and baking soda to get the
three critical properties within range, and a Rift Lake product (such as Kent
Rift Lake Trace Elements®) OR a marine salt (such as Instant Ocean®) to provide
additional trace elements. Some people prefer to stick with products specially
formulated for the Rift Lakes, while others have had great success with marine
salt. Incidentally, I have heard that marine salt is particularly beneficial in
Go with off-the-shelf products for
everything. There are quality products offered by Kent and Seachem (for
example) that deal with the basic chemistry, buffering and trace elements. When
combined into one product, it is sometimes referred to as cichlid salt. With
the information contained herein, you should be able to read the labels on
these products and have a better understanding of what they are supposed to do.
Test your water to be sure they are living up to their claims.
Other Conditions to Monitor: Be sure that
you have a good understanding of the nitrogen cycle. A properly cycled aquarium
should test zero for ammonia and nitrites, but nitrates slowly build up in your
aquarium and should be monitored. Nitrates are kept in check with regular
partial water changes, and are not really so much of a water chemistry issue as
a water quality one.
Provide sufficient surface agitation to
oxygenate your tank water and allow CO2 to escape.
Maintain a constant temperature in your
aquarium. The acceptable range is 74*-81*F, and many experienced hobbyists
recommend something in the mid-range, around 76-78*F. High temperatures speed
up metabolism and can result in more aggression. Invest in a quality heater to
avoid disasters such as overheating or failure. A good thermometer is important
too. Do not rely solely on the thermometer on the heater. I look at my thermometer
often to be sure the heater is working correctly. By doing so, I once averted
potential disaster when an inexpensive heater failed to shut off after the set
temperature had been reached. Lastly, be sure to match the tank water
temperature when making water changes to avoid stressing your fish.