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?

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Your fish live in it

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Are supported by it

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Receive their oxygen from it

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And excrete in it

Water Quality – Why Is It Important?

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Water quality factors influence and interact with each other

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What may cause problems in one situation may be harmless in another

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Influences effectiveness/toxicity of treatments

Water Quality – Why Is It Important?

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Most disease problems can be avoided with proper management of water quality

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This includes maintaining water quality at a level that provides an environment conducive to fish health and growth

Water Quality Variables

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Temperature

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Dissolved oxygen

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Total ammonia-nitrogen, NH 3 , NO 2

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Alkalinity

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Hardness

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pH

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Carbon dioxide

Water Quality Variables Temperature

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For each 10 °C (18°F) rise in temperature the metabolic rate doubles

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Controls the reaction rate of chemicals

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Influences solubility of gases in water

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Influences toxicity of ammonia and therapeutants

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Optimum temperature for tilapia growth is 85-88 °F

Water Quality Variables Dissolved Oxygen

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First limiting factor for growth and fish health

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Solubility decreases with increasing temperature and elevation

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Respiratory rate increases with increasing temperature, activity and feeding

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In general the minimum DO should be ≥ 60% of saturation or ≥ 5 ppm (mg/L)

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> 2 ppm in biofilter effluent

Water Quality Variables Total Ammonia-Nitrogen

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Usually the second limiting factor – nitrogenous waste: feces & feed

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TAN includes ammonium ion (NH 4 + ) and ammonia (NH 3 )

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The proportion of NH 3 increases with increasing temperature and pH

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< 0.05 mg/L NH 3

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< 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

___________________________________________ 50 º 0.19 1.83 15.7

68 º 86 º 0.40

0.80

3.82

7.46

28.4

44.6

The Nitrogen Cycle Water plants Algae Food Excess food Fishes Urine Feces Urea Peptides Amino acids Ammonia (NH )

Time Required for Bio-Filter to Mature

0.8

0.6

Ammonia (mg/l) 0.4

0.2

0.0

2 NH 3 NO 2 NO 3 6 10 14 Time in Days 18 22 0 8 6 4 Nitrites & Nitrates (mg/l) 2

Water Quality Variables - Alkalinity

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Is the buffering capacity of water – absorbs acids and/or bases

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High alkalinity prevents wide pH fluctuations

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Maintain levels between 75-120 mg/L as CaCO 3

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7 grams of alkalinity consumed by 1 gram of NH 3

Effects of pH on Various Buffers Percent of Total CO 2 100 Free CO 2 HCO 3 = CO 3 50 0 4 5 6 7 8 pH 9 10 11 12

Water Quality Variables

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Hardness

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pH

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Carbon dioxide 50 – 100 mg/L as CaCO 3 7 – 8 < 20 mg/L

Water Quality Variables Total Dissolved Gases Supersaturation caused by:

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leaking water lines

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air leak on low pressure side of pump

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source of water

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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

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Poor water quality

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Environmental conditions

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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% M O R T A L I T Y 0% Peracute Time Acute Chronic 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:

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DO level

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Metabolic rate of the fish

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Amount being fed

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Pathogen load

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Water exchange rate

Management Recommendations

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Maintain water quality within suggested guidelines

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Maintain fish loadings at optimum levels of 1/4 to 1/3 lb./gallon (1/2 lb./gallon maximum)

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Monitor water quality on a regular basis/keep good records

Management Recommendations

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Low DO: increase aeration; stop feeding

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High CO 2 : increase aeration; add air stripping column

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Low pH: add sodium bicarbonate; reduce feeding rate; check ammonia & nitrite

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High NH 3 : exchange system water; reduce feeding rate; check biofilter, pH, alkalinity & DO in biofilter

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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

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~ 300 square feet biofilter material per 100 lbs. fish

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Add 0.125 to 0.167 lbs. baking soda/ 100 gallons to maintain alkalinity

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Add 0.275 to 0.413 lbs salt/100 gallons to maintain chloride levels of 200 – 300 ppm

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Do not make any rapid changes to any WQ parameter, except to increase DO

Resources

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SRAC Publications: http://www.msstate.edu/dept/srac/publicat.htm

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Hach WQ test kits: http://www.hach.com/

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LaMotte WQ test kits: http://www.lamotte.com/

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Equipment Suppliers:

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http://aquaticeco.com/

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http://www.tecinfo.com/~aqcenter/

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Eagar, Inc. 1-800-423-6249