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Water Quality for Aquaponics Systems
Jen HoldsworthAquaponics Facilities Manager
Pentair Aquatic Eco‐Systems, Inc.Apopka, FL
Aquaponics Misconception
• Fish make waste + Plants clean water = Magic!
• Not exactly how it works
• Biological and Mechanical filtration required for bacterial transformation
Keys to a Successful Aquaponics System
• Efficient Solids Removal• Proper sizing: filtration, aeration, plumbing, fish to plant ratio• Improper filtration and improper sizing lead to poor solids removal, excess nutrient build‐up, poor water quality, poor production, fish and plant death
Nitrification and Bacterial Transformation
• Fish excrete ammonia through their gills and through their waste• This ammonia must go through the nitrification process to be made into a usable form for plants to uptake
• Ammonia oxidizes, turns into Nitrite• Nitrite oxidizes, turns into Nitrate• Nitrate is taken up by plants
Mechanical Filtration
• Solids must be removed from the system
• Circulation Pumps• Swirl separators • Drum Filters• Filter Socks• Cleaning of media beds
http://aquaponics.hunterinstitute.wikispaces.net/The+Nitrogen+Cycle
Biological Filtration
• Bacteria need some type of media to cling to in order to complete nitrification process
• The more surface area that is available, the more efficient the process
• Examples of biological filtration media:• Matala mats• Kaldnes Media• Pea Gravel• Lava Rock
Acceptable Ammonia Levels
• Ammonia will be present during initial system start‐up• After a few weeks should be as close to 0 as possible
• Ammonia buildup in the system after it is established indicates that solids are not being removed adequately
• If ammonia is not removed from the system, it can lead to fish death
Acceptable Nitrite Levels
• Ammonia will transform into Nitrite, and will be present during initial system start‐up
• After a few weeks should be as close to 0 as possible
• High nitrite levels can also cause fish death
Acceptable Nitrate Levels
• An indicator that a system has fully cycled is when ammonia and nitrite are no longer present
• Nitrate is important because this is the usable product that plants remove from the system to grow
• Acceptable nitrate levels 5‐100ppm depending on fish species and number of plants in the system
• Some fish are more tolerant of high nitrates and poor water quality than others
Acceptable Nitrate Levels
• Low nitrate levels can indicate not enough food going into system to support plants
• High nitrate levels can indicate too few plants in the system, or poor filtration‐ solids not being removed
• If nitrates are too high, plants will not make fruit, can also cause fish death
Dissolved Oxygen
• Fish require oxygen to breathe• Plant roots require oxygen to grow, will not tolerate stagnant water for long periods
• Dissolved oxygen level read in Percentage or Milligrams/Liter• Acceptable dissolved oxygen can range from 30‐100% or 5‐8Mg/L depending on fish species tolerance
Dissolved Oxygen Variables
• Readings will vary throughout the day• Normally highest in the morning• May decrease dramatically after feeding• It is possible for D.O. to be too high‐ over 150% can burn fish gills and cause other problems
• Important to monitor D.O. level multiple times a day
• Regulate D.O. levels with air pumps and diffusers, blowers, oxygen cone
• Higher stocking densities require increased oxygen levels
Backup Oxygen Supply
• Tanks with a high density of fish can be completely depleted of oxygen in a matter of minutes‐be prepared!
Temperature
• Temperature effects fish respiration rates, pH, and dissolved oxygen
• Lower air and water temperatures = higher dissolved oxygen levels
• Higher air and water temperatures = lower dissolved oxygen levels
• Desired temperatures vary by fish species
• Warmer climates create lower D.O., must compensate for this
pH
• pH measures acidity or basicity of water• Below 7 is acidic• Above 7 is basic
• In general plants like slightly lower pH, fish like slightly higher pH
• Ideal pH to strive for to have happy fish and plant is about 6.7
Stabilizing pH
• pH tends to decrease over time due to biofiltration and alkalinity comsuption• Low pH can lead to decreased nitrification• Must add chemical components to raise pH
• Calcium carbonate• Potassium carbonate • Liquid or powder forms
• pH changes throughout the day, should be checked one to two times a day after cycling
• High pH combined with high temperature can lead to high ammonia levels
Alkalinity
• The buffering capacity of water to neutralize acid
• Ideal alkalinity level 100‐200 ppm
• Low alkalinity or non‐buffered water causes pH swings
Calcium
• Calcium additives help stabilize pH and are also taken up by plants• Calcium deficiency can be associated with low pH• Usually added to the system either daily with a doser, or 1‐3 times a week depending on system readings
• Ideal calcium level 80‐150ppm
Iron
• Iron is beneficial for the plants• Keeps plant leaves a healthy green color• Yellow leaves indicate iron deficiency • Some plants show deficiencies earlier than others
• Ideal Iron level 2‐3.5ppm
Potassium
• Indicators of potassium deficiency:• Brown or curled leaf edges• Yellowing between veins• Purple spots under leaf
• Ideal potassium 50‐100ppm depending on plant type
How to monitor your Water Quality
• Test kits, titration methods• Computer probe monitoring• Hand‐held computer probes
How often to Check
• During initial setup, Ammonia, Nitrite, Nitrate, pH should be monitored daily
• After, Ammonia, Nitrite, Nitrate 1‐2x per week• pH daily• Calcium and Iron weekly
Identifying Nutrient Deficiencies
• Iron deficiency usually first to present itself, followed by calcium, then potassium
• Indicator plants
• Test kits• System additives
• Internet research• County extension agents
System Design and Water Quality
Pump size
• Undersized pump = poor circulation/flow, poor solids removal, excess nutrient buildup
• Oversize pump = high energy consumption
Aeration
• Poor aeration = low fish and plant density, poor plant growth
Tanks
• Rectangular tanks = poor solids removal
• Surface drain = poor solids removal
Filtration
• Lack of filtration or undersized filtration = poor solids removal, poor water quality
Nutrient Deficiencies
• Lack of water quality monitoring = nutrient deficiencies
Questions?