What do Fish Want??
The importance of Water Quality
and Testing Water
Original by Amy Gerhardt
Modified by Georgia Agricultural Education
Curriculum – July, 2002
Topics of Importance
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Components of Water
What do fish really want??
Ammonia
Nitrites
Nitrates
Dissolved Oxygen
Components of Water
• Key nutrient ions
• Phosphates, nitrates
• Dissolved Gases
• Oxygen, Carbon dioxide
• Trace ions
• Copper, iron, zinc, etc.
What do Fish Want??
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Low ammonia and nitrate levels
Chemically clean water
Correct water pH and temperature
Low levels of organic pollution
Stable conditions in water
Ammonia and Water Quality
• Ammonia is extremely toxic and even
relatively low levels pose a threat to fish
health.
• Fish continually excrete ammonia directly into
the surrounding water via special cells in the
gills.
• In a natural environment, such as seas, lakes
and rivers, it would be immediately diluted to
harmless levels.
• However, in ponds, levels can rapidly rise to
dangerous levels unless it is constantly
removed, usually by biological filtration.
• Additional amounts are produced from
decomposing fish food and fish waste
• Ammonia irritates gills, restricting the water
flow over the gill filaments, causing
respiratory problems and stress
• Fish rub against solid objects to relieve
irritation, without water testing it would be
very easy to wrongly conclude the fish had a
parasite problem.
• The fish response to toxic levels – loss of
appetite, laying on the pond bottom with
clamped fins, or gasping at the water surface if
the gills have been affected.
Nitrites and Water Quality
• Nitrite (NO2-) is formed when bacteria oxidizes
ammonia produced by fish and decomposing
organic matter.
• Prolonged exposure to low levels can lead to
stress, ulcers and fin rot
• The main danger: transported across the gills
and into the fish’s bloodstream which is
unable to move nitrates and fish suffocates
• At low levels the fish may rub against solid
objects or ‘flash’, gills will be pale tan to dark
brown in color, gasping at the water surface.
• Nitrogen cycle changes nitrites into nitrates,
2000 times less toxic to trout
Dissolved Oxygen and Water Quality
• Process of photosynthesis effects amount of
oxygen in water (20 - 30 times less oxygen in
water than air)
• As temperature increases, DO decreases
• Causes decrease in growth and reproduction
• Solutions to low level:
– Stop feeding to increase organic material
– Change partial water
– Decrease temperature slowly