Aquatics - Water Quality

?

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
1 of 10

Oxygen

  • 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.
2 of 10

pH

  • 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
  • pH = -log[H3O+]
  • pH = -log [H+]
3 of 10

Nitrification

  • NH3 + 2O2 --> NO3- + 2H+ + H2O
  • 2H+ lowers pH
4 of 10

Photosynthesis

  • CO2 ⇌ H2CO3 ⇌ HCO3- ⇌ CO32-
  • Overall increases pH
5 of 10

Water Hardness

  • 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-/CO32-
  • Soft = low GH, low KH, low pH
  • Hard = high GH, high KH, high pH
6 of 10

Salinity

  • 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
7 of 10

Chlorine and Chloramine

  • 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
8 of 10

Phosphates

  • 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
9 of 10

Calcium

  • 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
10 of 10

Comments

No comments have yet been made

Similar Other resources:

See all Other resources »See all Animal Management resources »