In any given area the water quality is determined by local conditions. Pure rain water starts to absorb
pol utants even as it fal s through the atmosphere. As it permeates through the soil and lies as ground
water, its chemical composition is affected by the nature of the earth’s strata in the locality and the
level of contaminants these contain. The various treatments that are used to produce pure drinking
water and the mains and pipes that carry the water to our homes can also contribute elements such as
chlorine, copper and zinc that are harmful to aquarium life. Due to these many influences, no two
types of tap water are alike - and vast differences often occur between neighboring towns. The
chemical and biological processes in an aquarium bring about stil further changes in the water quality.
In order for the flora and fauna to thrive, the conditions in the aquarium have to be suitable and must
correspond as closely as possible to those of their natural habitat. The biological balance and hence
the wel -being of fish and plants depends fundamental y upon the quality of the water in which they
With the TetraWHVW Laborett you wil have a reliable and accurate means of measuring the general
hardness, carbonate hardness, pH value, nitrite and carbon dioxide content of your aquarium water.
The general hardness of water is determined by the concentration of calcium and magnesium salts.
Where the level of these salts is high, the water is classified as hard and when it is low, as soft. A
favorable GH value at which most ornamental fish can be kept, is between 6° dH and 16° dH (°dH =
As wel as the calcium and magnesium salts already mentioned, almost every type of water contains
further salt components, such as bicarbonates - their levels in the water are indicated by the KH-value.
The bicarbonates have an important task to fulfil in the aquarium, acting as a pH-buffer and thus
preventing a drastic or sudden change in the pH value, as in the case of an acid col apse. Due to the
close interaction between the KH and pH values, the carbonate hardness also has a direct influence
on the wel being of al the organisms in the aquarium. A KH value between 3° dH and 10° dH is
general y recommended though fish from the East African Rift lakes (Malawi and Tanganyika) are
adapted to living with higher levels of carbonate hardness.
The pH value is calculated from the total amount of acidic and basic substances dissolved in the water
that could either acidify the water or turn it alkaline. Chemical y pure water has a pH value of and is
designated as neutral. In it the acid and alkaline components are equal y balanced. The more acids
that are present, the lower the pH value. The more basic components present, the higher the pH value
rises. A sudden lowering of the pH value can occur, for instance, in very soft water if the bicarbonate
(KH value) buffer is used up. Al fish, plants and micro-organisms are very sensitive to drastic changes
in pH and for this reason you should test the pH value at least once a week. A pH value of between
6.5 and 8.5 wil suit almost every species of fish encountered in the freshwater aquarium. Fish
originating from blackwater rivers prefer soft water with pH values between 6.0 and 7.5 whilst East
African cichlids find values in the range between 7.5 and 8.5 and a high carbonate hardness very
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Due to fish excreta, decaying plant residues and left-over food, nitrogen compounds, which are
degraded in a series of steps, find their way into the aquarium water. The first stage of this process is
the formation of either toxic ammonia or non-toxic ammonium. The pH value greatly influences the
amount of ammonia or ammonium produced: with pH values of below 8.0, non-toxic ammonium wil
mainly be formed; if the pH value exceeds this figure, however, ammonia wil mainly be produced. A
long-term ammonia content of just 0.1 mg/l can even be harmful to sensitive fish. Concentrations of as
little as 0.5 to 1 mg/l can have a lethal effect on some fish.
In the second stage, ammonia and ammonium are broken down into nitrite with the aid of
Nitrosomonas bacteria. Nitrite, however, is also poisonous and extremely harmful to ornamental fish.
Ensure your aquarium has a biological y active filtration system – only aquaria with an intact filtration
system have maximum nitrite concentrations of 0.3 mg/l. The nitrite content should not exceed 0.8
mg/l over a long period of time since a content as low as 1.6 mg/l can be harmful to your freshwater
In the final stage of degradation, Nitrobacter bacteria turn nitrite into nitrate, which is relatively
harmless. One function of nitrate is to provide plant with nutrients. Excessive concentrations, however,
are harmful to your ornamental fish and promote the tiresome growth of algae.
Nitrate contents of up to 25 mg/l are considered harmless in aquarium water. Should the nitrate
content rise to between 25 mg/l and 100 mg/l, particularly in marine water, a partial water change is
recommended. Water is considered to be contaminated if nitrate values exceed 100 mg/l. In this case,
Oxygen is essential in the aquarium for a number of reasons – it forms the basis for the existence of
both fish and plants. During the day, the underwater flora absorbs carbon dioxide (CO2) and emits
oxygen (O2) through photosynthesis. In order to breathe, the fish absorb oxygen through their gil s.
Oxygen is also essential to al bacteria, especial y those that are responsible for degrading nitrogen in
the aquarium. At night, the process is reversed – the aquatic plants emit carbon dioxide and absorb
oxygen. This is why the oxygen content can be lower in the morning than in the evening if the
aquarium is not ventilated. The maximum ability of the water to absorb oxygen is known as the
saturation concentration (measured in mg/l), which is dependent on the water temperature and the salt
content. Please ensure that the fol owing saturation values do not fal below 80% of the given value. If
oxygen levels are too low for a long period of time, the resulting oxygen deficit can lead to your
ornamental fish becoming more prone to diseases.
Oxygen saturation concentration of freshwater. Corresponds to 100% saturation.
Oxygen saturation concentration of marine water of varying densities. Corresponds to 100%
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1. The temperature of the water must be between 20° and 30° Celsius. Samples taken outside this
2. Rinse the Tetra test vial with aquarium water.
3. Fil the test vial with 5 ml of aquarium water.
4. Hold the reagent bottle containing test liquid 1 over the test vial and add 14 drops to it. Careful y
5. Hold the reagent bottle containing test liquid 2 over the test vial and add 7 drops to it. Careful y
6. Hold the reagent bottle containing test liquid 3 over the test vial and add 7 drops to it. Careful y
7. Close the test vial and shake wel . Leave the vial to stand for 20 minutes at room temperature.
8. Compare the shade of the liquid with the color scale and read off the measurements.
9. On completion of the test, clean the test vial using tap water.
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1. Rinse the test vial with aquarium water.
2. Fil the test vial with 5 ml of aquarium water.
3. Hold the reagent bottle containing the nitrate 1 test liquid over the test vial and careful y add 14
4. Now add 7 drops of the nitrate 2 test liquid to the vial and careful y shake it.
5. Using the measuring spoon, add 1 spoon of the test powder to the vial, close it and shake wel for
6. Add 7 drops from the reagent bottle containing the nitrate 3 test liquid to the vial, gently shake it
and leave it to stand for 10 minutes for the color to form.
7. Compare the shade of the liquid with the color scale and read off the measurements. When
reading the measured value, take care that the vial is kept upright and approx. one finger's
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Tip: The oxygen content in non-aerated aquariums wil be lower in the morning than over the day. The
reason for this is that the plant organisms stop producing O2 at night and actual y make use of oxygen
themselves. We therefore recommend taking O2 measurements in the morning.
1. Rinse the test vial with aquarium water.
2. Fil the test vial to the 15 ml mark with aquarium water.
3. Hold the O2 reagent bottle 1 over the vial and add 5 drops to it.
4. Hold the O2 reagent bottle 2 over the vial and add 5 drops to it.
5. Immediately put the lid on the test vial and turn it upside down. A deposit is formed (fine,
undissolved particles that cloud the liquid). Vials containing freshwater should be left to stand for
30 seconds, whereas marine water requires 5 minutes.
6. Reopen the test vial, hold the O2 reagent bottle 3 over the vial and add 5 drops to it.
7. Immediately put the lid on the test vial and turn it upside down twice. The deposit dissolves,
8. In order to read the oxygen content, compare the shade of the liquid with the color scale and read
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There are also a number of general tips that al aquarium owners should know about to help reduce
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Avoid having too many fish in your aquarium. Also ensure that the fish are not too large in
It is better to feed the fish smal portions several times a day rather than just one large helping a
day. Only give the fish the amount of food they can eat within a few minutes. We recommend the
proven Tetra range of quality fish foods.
Make sure that you have a filtration system suited to both the size of the aquarium and the number
of fish contained in it. In a newly set up tank, the filtration system wil take approximately 4 to 6
weeks to become biological y activated. Use biological filter media, e.g. foam or depot filters that
enable actively degrading bacteria to settle on them. The filter material must be cleaned regularly
to prevent it from silting or blocking up.
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Make sure that you have dense, healthy plant growth. Thriving plants take nitrate out of the water
and thus stabilize the biological state of the aquarium. Use nitrate- and phosphate-free fertilizers
such as Tetra3ODQW PlantaMin, Tetra3ODQW Crypto fertilizers and Tetra3ODQW InitialSticks, because
these supply the aquatic plants with balanced quantities of micro- and trace elements.
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• Fol ow the general advice on reducing contaminants.
• Ask your local dealer about suitable methods to reduce water hardness, e.g. ion exchangers.
• An excessively high pH value can easily be lowered by using Tetra$TXD pH/KH Minus or by
adding carbon dioxide (CO2) fertilizer in the form of Tetra CO2 Optimat. The CO2 acidifies the
water, while at the same time improving plant growth.
• If the pH value is too low, this can be regulated precisely and on a long-term basis with Tetra$TXD
pH/KH Plus, which simultaneously raises the carbonate hardness of the water. In general, the pH
value of the water can also be raised by driving off excess CO2, e.g. by aerating the aquarium
using a TetraWHF Air Pump and air stone. Overnight aeration of the aquarium is general y
recommended. For further information, please refer to the specialist journals and literature. If you
have any specific problems, your local dealer wil be happy to give you helpful advice.
• If the ammonia content is too high, immediately change half of the aquarium water, fol owing the
information given above on reducing contaminants.
• Check the filtration system and measure the O2 content.
• Reduce the biological pH value by adding CO2.
• Immediately carry out a partial water change (approx. 50%).
• Check the filtration system and measure the O2 content.
• Fol ow the general advice on reducing contaminants.
• If the nitrate content in freshwater and marine water exceeds 100 mg/l and 50 mg/l, respectively,
immediately carry out a partial water change (approx. 50%).
• Fol ow the general advice on reducing contaminants, since an excessive level of nitrate is a clear
and sure sign of impurity and the gradual contamination of the aquarium water. Pay particular
attention to healthy plant growth – thriving plants remove nitrate from the water, stabilizing the
• In marine aquaria, algae, e.g. filamentous algae and the decorative leaf-like algae (e.g.
Caulerpales) can be used to denitrificate the water.
• Aerate the tank as an immediate measure.
• Aerate the tank at night using an air pump and an air stone (medium-term measure).
• Use an air-powered filtration system (e.g. Tetra Filter).
• Ensure the water is circulated sufficiently, e.g. by the filter.
• Improvement and promotion of plant growth by adding CO2 and fertilizer, e.g. Tetra3ODQW
• Check the filter (silting, excessive use of oxygen).
• Fol ow the general advice on reducing contaminants.
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PATIENT HANDOUT A Common sense approach To lower urinary tract hypersensitivity in women What you can do to help relieve your symptoms T he purpose of this handout is to provide information that can Dietary irritants to the urinary tract to avoid help you discover what you are ingesting or doing that may becontributing to your recurrent irritative voiding symptoms and whatCe
The Australian Society for Medical Research ASMR Medical Research Week® June 3 - 11 Media release – Embargoed: 12.30pm, Wednesday 8June 2005 Expert says genetic technology could enhance our children’s well-being “We have a moral obligation to treat and prevent disease” International ethics expert, Professor Julian Savulescu says that we are morally oblige