Transcript Water Quality Power Point - What you need to know to keep

WATER QUALITY
What You Need To Know
To Keep Your Fish Alive
Gary Fornshell, University of Idaho
Terry Patterson, College of Southern Idaho
To a great extent, the
success or failure of
fish culture is
determined by water
quality
Water Quality – Why Is It Important?
• Your fish live in it
• Are supported by it
• Receive their oxygen from it
• And excrete in it
Water Quality – Why Is It Important?
• Water quality factors influence and interact
with each other
• What may cause problems in one situation
may be harmless in another
• Influences effectiveness/toxicity of
treatments
Water Quality – Why Is It Important?
• Most disease problems can be avoided
with proper management of water
quality
• This includes maintaining water quality at a
level that provides an environment
conducive to fish health and growth
Water Quality Variables
• Temperature
• Dissolved oxygen
• Total ammonia-nitrogen, NH3, NO-2
• Alkalinity
• Hardness
• pH
• Carbon dioxide
Water Quality Variables
Temperature
• For each 10°C (18°F) rise in
temperature the metabolic rate doubles
• Controls the reaction rate of chemicals
• Influences solubility of gases in water
• Influences toxicity of ammonia and therapeutants
• Optimum temperature for tilapia growth is 85-88 °F
Water Quality Variables Dissolved
Oxygen
• First limiting factor for growth and fish health
• Solubility decreases with increasing
temperature and elevation
• Respiratory rate increases with increasing
temperature, activity and feeding
• In general the minimum DO should be ≥ 60%
of saturation or ≥ 5 ppm (mg/L)
• > 2 ppm in biofilter effluent
Water Quality Variables
Total Ammonia-Nitrogen
• Usually the second limiting factor – nitrogenous
waste: feces & feed
•TAN includes ammonium ion (NH4+)
and ammonia (NH3)
• The proportion of NH3 increases with increasing
temperature and pH
• < 0.05 mg/L NH3
• < 0.5 mg/L nitrite-N (NO-2)
,
Percent of Total Ammonia
in the Un-Ionized Form at
Various Temperatures and pH
percent Ammonia
Temperature (ºF)
(pH) 7.0
8.0
9.0
___________________________________________
50º
0.19
1.83 15.7
68º
0.40
3.82
28.4
86º
0.80
7.46
44.6
The Nitrogen Cycle
Water plants
Food
Excess
food
Algae
Nitrate (NO 3 )
Fishes
Urine
Feces
Urea
Nitrite (NO 2 )
Ammonia
(NH 3 )
Peptides
Amino acids
Time Required
for Bio-Filter to Mature
0.8
8
NO 3
0.6
Ammonia
(mg/l)
NH 3
NO2
6
0.4
4
0.2
2
0.0
0
2
6
10
14
18
Time in Days
22
Nitrites &
Nitrates
(mg/l)
Water Quality Variables - Alkalinity
• Is the buffering capacity of water –
absorbs acids and/or bases
• High alkalinity prevents wide pH fluctuations
• Maintain levels between 75-120 mg/L as CaCO3
• 7 grams of alkalinity consumed by 1 gram of NH3
Effects of pH on Various Buffers
Percent of Total CO 2
100
-
Free CO 2
=
HCO3
CO 3
50
0
4
5
6
7
8
pH
9
10
11
12
Water Quality Variables
• Hardness
50 – 100 mg/L as CaCO3
• pH
7–8
• Carbon dioxide
< 20 mg/L
Water Quality Variables
Total Dissolved Gases
Supersaturation caused by:
• leaking water lines
• air leak on low pressure side of pump
• source of water
• mixing cold and hot water
Recommended total dissolved gas pressure <104%
Water Balance in Freshwater Fish
Water
Salts
Ammonia
Large quantities
of dilute urine
Stressors
• Poor water quality
• Environmental conditions
• Improper handling
Most Fish Diseases
Are Stressed Mediated
Stress is a physiologic state caused by a procedure,
environmental condition or other factor which interferes with
the fish’s ability to maintain a “normal” state. It extends the
adaptive responses of an animal beyond the normal range or
which disturbs the normal functioning.
Low Level Mortality
100%
Peracute
M
O
Acute
R
T
A
L
Chronic
I
T
Y
0%
Time
Usually the first sign of water
quality/environmental
problems
Loading Effects
Number of fish which can
successfully live and grow
in a given amount of water
depends on:
• DO level
• Metabolic rate of the
fish
• Amount being fed
• Pathogen load
• Water exchange rate
Management Recommendations
• Maintain water quality within suggested guidelines
• Maintain fish loadings at optimum levels of 1/4 to
1/3 lb./gallon (1/2 lb./gallon maximum)
• Monitor water quality on a regular basis/keep good
records
Management Recommendations
• Low DO: increase aeration; stop feeding
• High CO2: increase aeration; add air stripping
column
• Low pH: add sodium bicarbonate; reduce feeding
rate; check ammonia & nitrite
• High NH3: exchange system water; reduce feeding
rate; check biofilter, pH, alkalinity & DO
in biofilter
• High nitrite: exchange water; reduce feed; add 6
ppm chloride per 1 ppm nitrite; check
biofilter, pH, alkalinity & DO in biofilter
Good Stuff To Know
• ~ 300 square feet biofilter material per 100 lbs. fish
• Add 0.125 to 0.167 lbs. baking soda/ 100 gallons to
maintain alkalinity
• Add 0.275 to 0.413 lbs salt/100 gallons to maintain
chloride levels of 200 – 300 ppm
• Do not make any rapid changes to any WQ
parameter, except to increase DO
Resources
• SRAC Publications:
http://www.msstate.edu/dept/srac/publicat.htm
• Hach WQ test kits: http://www.hach.com/
• LaMotte WQ test kits: http://www.lamotte.com/
• Equipment Suppliers:
• http://aquaticeco.com/
• http://www.tecinfo.com/~aqcenter/
• Eagar, Inc. 1-800-423-6249