Aquatics - Water Quality - Revision Cards in Other Other

Water Testing

Many types of test kits
- some are more accurate than others
- aquarists have their own favourite
- range in price for private and public aquariums

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why do we need to measure oxygen?
- fish need oxygen in order to respire
does warm or cold water contain more oxygen?
- cold as molecules are moving less and the oxygen makes it to the surface slower
Measured in mg/l or %, and usually measured as dissolved oxygen (DO)
Can be measured with a test kit or DO probe
- A DO probe is an electric piece of equipment where you put it into the water and it gives you the oxygen reading
Dissolved oxygen should ideally be 80% to 100% within the tank
If the oxygen level is too low the fish can't breathe
- if the oxygen level is slightly too low for a long period of time it can cause stress
- lack of oxygen is caused by overstocking, lack of water movement, lack of plants, and if the tank is unclean the bacteria will use more oxygen.
When oxygen levels are too high it is called supersaturation
- If oxygen exceeds 100% there will be air bubbles in the water which can stick to the gills of fish, meaning the fish won't be able to absorb oxygen.
- The entire tank can be killed in 15 minutes by supersaturation.

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How acidic or alkali the water is
- to know what pH the tank needs to be look at the pH in the fish's natural habitat
- needs to differ between fresh and marine water
usually between 7-8
- freshwater may be 6
- saltwater may be closer to 8
important to monitor as scale is logarithmic
- small number changes actually means massive chemical changes
pH of planted aquariums increase throughout the day
some fish are more sensitive to pH

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The measure of dissolved minerals in the water.
- hard water = more dissolved minerals
Related to pH as minerals buffer pH, they stop the pH from dropping
- can't use pH alone to determine water hardness
- buffering: better capability of keeping control
Hard water has a higher pH and soft water has a lower pH
check to see the hardness of the water you are using
water additives can be used to achieve the correct level of hardness
if using RO (reverse osmosis) water you will need to add minerals for the buffering properties
- reverse osmosis water is good for coral reef tanks
GH = general hardness, Ca²⁺, Mg²⁺
KH (alkalinity) = carbonate hardness, HCO₃^-/CO₃^2-
Soft = low GH, low KH, low pH
Hard = high GH, high KH, high pH

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how salty the water is?
measured in parts per thousand (ppt) or specific gravity
some sites use natural seawater, some make their own
- generally, use natural seawater if by the coast
if mixing salt water, reverse osmosis water is mixed with specially designed salt to correct salinity
- should be gradually added to the system
- may sink to the bottom
marine range is between 30-36 ppt, freshwater is 0ppt, brackish is 10-14 ppt
different salinities can be used for treatment
- saltwater fish parasites can be killed in freshwater
- using a freshwater dip
  - saltwater fish put in freshwater for a few minutes
  - parasites shocked
  - freshwater dips can stress saltwater fish

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added to tap water by the water board to kill off anything that may make water unsafe
chlorine and chloramine are very dangerous for fish so must be removed
can be removed by using reverse osmosis water, agitation (such as stirring the water), or chemicals, or leaving the chlorine to dissipate over time
- a good idea to keep chemical methods on hand in case of an emergency
chemicals are easily bought from pet shops

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phosphates are a chemical found in all living organisms
enter the aquatic system from water rock or sunstrate, frozen foods and carbon
high levels cause excessive algae growth and will stunt coral growth
should be kept below 0.05 parts per million
excess phosphates should be removed by water changes, skimming or using absorbing media
- absorbing media can become full and leach phosphates back into the water

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coral absorbs calcium from the water
important in reef aquariums for coral growth
corals use up calcium as they build their 'skeleton' so it should be checked and replenished
- hard corals need more calcium than soft corals
demand will vary dependent on hard or soft corals
in a home aquarium should read between 400 - 450 parts per million
calcium supplements are available

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