Fish Management in
Aquaponics
William Lynch Jr.
Millcreek Perch Farm, LLC (owner)
Ohio State University Extension Program (retired)
Marriage of plant & fish production, hopefully
with few martial problems!
Plants depend on fish wastes for nearly all
nutrient requirements, but also bacteria to
transform ammonia / nitrite into nitrates readily
usable by plants.
Fish depend on bacteria to transform ammonia
/ nitrite into nitrates readily usable by plants so
as to minimize nitrogen compounds returning to
the fish production tanks.
Marriage of plant & fish production, hopefully
with few martial problems!
Plants depend on fish wastes for nearly all
nutrient requirements, but also bacteria to
transform ammonia / nitrite into nitrates
readily usable by plants.
Fish depend on bacteria to transform ammonia
/ nitrite into nitrates readily usable by plants so
as to minimize nitrogen compounds returning
to the fish production tanks.
Marketing
Potential Markets
Availability
Readily available sources in the
quantities you need when you
need them
Compatibility
Is the species of choice compatible
with the growth requirements of
plants & bacteria
Feed & Heating Considerations
Different costs for different species
Bluegill sunfish
Channel catfish
Goldfish / koi
Largemouth bass
Tilapia
Yellow perch
Goldfish / Koi
Yellow perch
Sunfish
Rainbow trout
Channel catfish
Largemouth bass
Source: 2012 USDA Census of Aquaculture
Species
Stocking
Food Fish*
Sunfish (Bluegill, Redear)
Channel Catfish
Goldfish / Koi
Largemouth Bass
Tilapia
Yellow Perch
* = HAACP Requirements May Be Needed
Ease of Growing Rank
Species
Stocking
Food Fish*
Sunfish (Bluegill, Redear)
5
4
2
Channel Catfish
Goldfish / Koi
Largemouth Bass
6
1
3
Tilapia
Yellow Perch
* = HAACP Requirements May Be Needed
Species
In Ohio
Sunfish
Channel Catfish
1-Day
Transport
Yes
Yes
Goldfish / Koi
Yes
Largemouth Bass
Yes
Tilapia
Yellow Perch
Overnight
Shipping
Yes
Yes
Choose between small (1-2 inch) or advanced
fingerlings (3-4 or 4-5 inch).
Amount of feed per day drastically different
between sizes – impacts nutrients available to
plants.
Always buy feed-trained fingerlings – you would
prefer not to have to feed train them yourself.
If possible, buy the upper 50% (length)
produced by the hatchery.
Do not buy the cheap runts, you will be sorry!
55 F
Warm weather plants
Cool weather plants
60 F 65 F 70 F
75 F 80 F 85 F
55 F
Warm weather plants
Cool weather plants
Nitrobacter
Nitrosomonas
60 F 65 F 70 F
75 F 80 F 85 F
55 F
60 F 65 F 70 F
75 F 80 F 85 F
Warm weather plants
Cool weather plants
Nitrobacter
Nitrosomonas
Bluegill
Channel catfish
Goldfish / Koi
Largemouth bass
Tilapia
Yellow perch
Best
5.5
6.0
6.5
7.0
Warm weather plants
Cool weather plants
Nitrobacter
Nitrosomonas
Bluegill
Channel catfish
Goldfish / Koi
Largemouth bass
Tilapia
Yellow perch
Best
7.5
8.0
8.5
Species
40-50%
Protein
$$$
Sunfish
Yes
Channel
Catfish
Goldfish/Koi
Largemouth
Bass
22-35%
Protein
$
High
Yes
Yes
Mod
Mod
Yes
Yes
Summer Winter
Cooling Heating
Mod
Yes
Tilapia
Yellow Perch
32-38%
Protein
$$
High
Mod
Water temps no more
than 3 F difference
Salt at 1-3 ppt
pH no more than
0.5 difference
Salt at 2-3 ppt
2-2.5 lbs per
100 gallons
Tank density no more than 0.5 pounds of
fingerlings per 5 gal. of water in static systems. If
small biofilter on isolation tank, can go higher.
Heavy aeration in no flow, isolation tank, monitor
oxygen hourly until readings stabilize.
Do not flow aquaponics system water thru
isolation tank, defeats the purpose of isolation.
Feed sparingly. Will ruin water quality unless
equipped with small biofilter.
Fish should remain in isolation for at least a
week, preferably 2 weeks before being placed
into the aquaponics system.
If isolation tank was a grow-out tank shut off
from the aquaponics system, simply turn on
valves to allow flow.
If fish are to be moved from isolation tank to a
separate grow-out tank ….
Be sure grow-out tank is nearly empty
Move isolation tank water and fish to grow-out
tank
Slightly open valve to slowly add aquaponics
system water very slowly until temps are equal.
Once acclimated, open valves and begin feeding.
Stress is the leading cause of fish death in
aquaculture
Stress can be severe, causing death within
minutes. Best example is a sudden low
oxygen event.
Chronic stress is longer term exposure to poor
living conditions, causing impairment to the
immune system.
A chronically stressed fish is eventually a
diseased fish and then soon a dead fish.
Poor water quality is the leading cause of
chronic stress.
A close aquaculture friend once told me : “A
Successful Fish Culturist is not successful because
he or she is a successful biologist, physiologist
etc.”;
“No, he or she is successful in large part because
that person is a successful water quality and
aquatic waste management specialist”;
“If you successfully degrade nitrogenous wastes
and uneaten food safely and therefore maintain
excellent water quality, the fish will take care of
themselves”.
* Can be toxic to fish
Solids Removed
Plants
Fish
Fish Wastes, Uneaten Feed
Nitrate (NO3)
Nitrobacter Bacteria
Ammonia* (NH3)
Nitrosomonas Bacteria
Nitrite* (NO2)
Retained in Tissues
30% N
32% P
Fish Feed
100% N
100% P
Solids
13% N
60-90% P
Effluent
70% N
68% P
Dissolved
87% N
10-40% P
Source: Chris Hartleb, UW-Stevens Point
Species
DO
(mg/l)
Temp
(F)
pH
Unionized
Ammonia
(mg/l)
Nitrite
(mg/l)
Sunfish
>4
68-80
7-8.5
< 0.01
< 0.8
Channel
Catfish
Goldfish/Koi
>4
70-90
7-8
< 0.05
< 0.8
>4
65-75
6-8
< 0.08
< 0.6
Largemouth
Bass
Tilapia
>4
68-80
7-8.5
< 0.01
< 0.8
>4
70-90
7-8
< 0.04
< 0.8
Yellow Perch
>4
70-76
7-9
< 0.02
< 1.0
Daily
Water Temperature
Dissolved Oxygen
pH
2-3 Times per Week
Ammonia
Nitrite & Nitrate
Monthly
Alkalinity / Hardness
Carbon Dioxide
SRAC has fantastic factsheets on water quality!
= air stones
Sump
Plants
Fish
Fish
Plants
Plants
Plants
Solids Clarifier
Tank
Oxygen / Temperature
Ammonia / Nitrite / Nitrate
If temperature is too low . . .
Turn up heaters
If oxygen too low in fish tanks . . .
More air stones in fish tanks and possibly plant
beds (bacteria in plant troughs need oxygen!)
Consider an air stone in the sump
If nitrite / ammonia compounds are measurable
in last plant trough . . . .
Reduce feed, as bacteria & plants not able to
remove the compounds fast enough.
If nitrogen compounds non-detectable . . .
Could feed fish more if desired for plants
Ad Libitum – feed as much as fish want in 15
minutes (also known as satiation feeding)
May be way in excess of what the bacteria /plant
community can handle
Fixed ration per day – typically 1.5-3% tank fish
biomass per day
Requires knowing numbers of fish in tank plus their
average weight. Done by subsampling weekly.
Labor intensive.
May still be way in excess of what the bacteria /
plant community can handle
Neither is well suited for aquaponics systems
Let the Ammonia / Nitrite / Nitrate Readings
Guide Feeding Rate
No ammonia / nitrite compounds at end of last
plant trough – you can feed fish more. Vice versa.
Oxygenate Those Bacteria!
Key to the ammonia to nitrite to nitrate cycle is a
well oxygenated, prolific bacteria community.
Plants are Guides too!
If nitrates are low, could grow more plants
If nitrates building up, back off fish feed a little.
Typically the first 6-10 weeks after
an aquaponics system is brought
online. And fish feeding has
commenced.
System contains very small, young
plants requiring few nutrients at
first but increases as plants grow.
Nitrosomonas / nitrobacter
community non-existent at first and
slowly develops.
Nearly 90% of fish problems &
mortality occurs in this period.
Elevated ammonia / nitrites will kill fish!
This 6-10 week period often has wild swings in
ammonia & nitrites as fish feeding begins.
You must monitor ammonia / nitrite levels daily
at the end of last plant trough. 2-3 times per
week thereafter.
Fish feeding is very little at first, often less than
0.1% tank biomass.
As described earlier, let those readings in the
last plant trough dictate feeding!
[email protected]
614-579-6381