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WATER QUALITY What You Need To Know To Keep Your Fish Alive Gary Fornshell, University of Idaho Terry Patterson, College of Southern Idaho.

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Presentation on theme: "WATER QUALITY What You Need To Know To Keep Your Fish Alive Gary Fornshell, University of Idaho Terry Patterson, College of Southern Idaho."— Presentation transcript:

1 WATER QUALITY What You Need To Know To Keep Your Fish Alive Gary Fornshell, University of Idaho Terry Patterson, College of Southern Idaho

2 To a great extent, the success or failure of fish culture is determined by water quality

3 Water Quality – Why Is It Important? Your fish live in it Are supported by it Receive their oxygen from it And excrete in it

4 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

5 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

6 Water Quality Variables Temperature Dissolved oxygen Total ammonia-nitrogen, NH 3, NO - 2 Alkalinity Hardness pH Carbon dioxide

7 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 °F Water Quality Variables Temperature

8 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

9 Water Quality Variables Total Ammonia-Nitrogen Usually the second limiting factor – nitrogenous waste: feces & feed TAN includes ammonium ion (NH 4 + ) and ammonia (NH 3 ) The proportion of NH 3 increases with increasing temperature and pH < 0.05 mg/L NH 3 < 0.5 mg/L nitrite-N (NO - 2 ),

10 Percent of Total Ammonia in the Un-Ionized Form at Various Temperatures and pH percent Ammonia Temperature (ºF) (pH) ___________________________________________ 50º º º

11 Water plants Food Excess food Fishes Peptides Amino acids Urine Urea Ammonia (NH ) Algae Nitrate (NO ) Nitrite (NO ) Feces The Nitrogen Cycle

12 Ammonia (mg/l) Nitrites & Nitrates (mg/l) NH NO Time in Days Time Required for Bio-Filter to Mature

13 Water Quality Variables - Alkalinity Is the buffering capacity of water – absorbs acids and/or bases High alkalinity prevents wide pH fluctuations Maintain levels between mg/L as CaCO 3 7 grams of alkalinity consumed by 1 gram of NH 3

14 Free CO HCO CO Percent of Total CO 2 3 -= 2 3 pH Effects of pH on Various Buffers

15 Water Quality Variables Hardness50 – 100 mg/L as CaCO 3 pH7 – 8 Carbon dioxide< 20 mg/L

16 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%

17 Water Balance in Freshwater Fish Salts Large quantities of dilute urine Ammonia Water

18 Stressors Poor water quality Environmental conditions Improper handling

19 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.

20 Low Level Mortality 100% MORTALITYMORTALITY 0% Peracute Acute Chronic Time Usually the first sign of water quality/environmental problems

21 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

22 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

23 Management Recommendations Low DO: increase aeration; stop feeding High CO 2 : increase aeration; add air stripping column Low pH: add sodium bicarbonate; reduce feeding rate; check ammonia & nitrite High NH 3 : 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

24 Good Stuff To Know ~ 300 square feet biofilter material per 100 lbs. fish Add to lbs. baking soda/ 100 gallons to maintain alkalinity Add to 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

25 Resources SRAC Publications: Hach WQ test kits: LaMotte WQ test kits: Equipment Suppliers: Eagar, Inc


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