This document discusses fertilization and supplementary feeding practices for smallholder fish farmers in Zambia. It covers applying organic manure like animal waste to ponds to stimulate plankton growth and create a natural food chain for fish. Maintaining green water color is best for tilapia production. Supplementary commercial or homemade feeds provide additional nutrition. Proper water quality monitoring and adjustments to fertilization rates are important. Signs of fish disease and strategies for health management are also outlined.

1. Presenter: Dr. Mary Lundeba
Climate-smart aquaculture
(CSA) for smallholder
fish farmers in Zambia:
26|May 2022

2. Fertilization and supplementary feeding
What is involved in fertilization of ponds?
 Application of organic manure, such as animal and compost manure to
the fish ponds
 Some of the examples of organic manure include chicken, duck, goat, pig,
cattle and compost manures
Compost and animal manure are easier to obtain and less expensive

3. The purpose of fertilization
 To create a food chain that will increase the productivity of the pond
 Nutrients added to ponds stimulate the production of plankton, which is a
natural food for fish
 Small fish will mainly feed on plankton in a fertilized pond
 Plankton is in two forms; plant form called phytoplankton and animal
form known as zooplankton
 Natural food in the pond is very small and hard to see

4. Purpose of fertilization
 The color of the pond water determines the presence of this natural food
 Usually, pond water can be green, brown, reddish or transparent
 Green colors indicate plankton productivity; green can range from
brownish green, yellow-green to bluish-green
 Brownish green suggests that the blooms have more zooplankton while
yellow and bluish green indicates the presence of phytoplankton

5. Purpose of fertilization
 Green water is the best for tilapia production
 When the green color is deep (dark green), it is a sign of over-fertilization
and corrective measures should be taken
 When pond water is transparent, it is a sign of non-fertilization or under-
fertilization and corrective measures should be taken

7. Supplementary feeds
 Commercial supplementary feeds (18% CP) can be used in combination
with fertilization
 Small fish will feed on plankton in a well-fertilized pond, and when they
grow larger supplementary feeds with a lower protein content should be
provided to the fish
 This method can be applied to extensive and semi-intensive systems of
culture with a stocking density of less than 5 fish/m2.

8. Supplementary feeds
 Fertilization alone cannot be enough to increase pond production because
of inadequate manures to fertilize the ponds
 Most farmers do not have enough animals
for adequate provision of organic manure
 It is important to complement fertilization
with supplemental feeds, which can be
commercial or farm/home-made
supplemental feeds

9. Supplementary feeds
You can formulate a farm/home-made feed with locally available ingredients
such as maize, millet, soybeans, sunflower cakes, cassava, trash fish, etc.

10. BMPs on fertilization and supplementary feeds
 Follow the instructions of the feed supplier for supplementary feed use
 Do not use compost cribs for fertilization, since these do not fertilize the
ponds effectively and reduce the productive surface area of the pond
Do not over-fertilize
 Maintain light green pond water
 If the water is green enough, do not apply additional manure (over-
fertilization will deplete dissolved oxygen)

11. BMPs on fertilization and supplementary feeds
 Organic manure should be free of chemicals, antibiotics or hormones
 Do not exchange the water in fertilized ponds or reduce the exchange rate
to the lowest level, unless there is an emergency situation
 If water is not kept in the pond, the effectiveness of the fertilizer decreases
 Fertilizers should be distributed evenly across the entire pond surface
once a week or if pond is already well fertilized, put manure the bags and
place in the pond

12. BMPs on fertilization and supplementary feeds
 Fertilize only on sunny days for easier breakdown of manure by bacteria
 Remove aquatic plants from the pond because aquatic plants
comparatively absorb more nutrients than phytoplankton
 Wean fish on pellets by providing small amounts of feed into the ponds
from the beginning of the 7th week to train fish to start consuming feed

13. BMPs on fertilization and water quality
 Water quality is very important for fish growth and health
 Poor water quality can negatively affect your fish farm and productivity
 Water quality for fish growth can be improved through fertilization
Critical parameters in the pond environment include:
Dissolved oxygen, temperature, pH, ammonia, transparency, and ‘water
color’ in relation to fertilization

14. BMPs on fertilization and water quality
Dissolved oxygen concentration:
 Recommended is 5.0 and 7.5 mg/L
Signs of low dissolved oxygen: gasping, fish the water surface, fish swim
sluggishly
 Check your ponds in the morning because DO is lowest in the early hours.
Why?
Temperature: Optimum growth for most tilapia species is achieved at 24°C–
30°C
 Temperature plays a critical role in fish reproduction, feeding rate, fish
growth, fertilization, dissolve oxygen concentration etc.

15. BMPs on fertilization and water quality
Transparency: Transparency is an indicator of water clarity
It can be measured using a secchi disk.
The best reading is from 30-45cm
“Water color’ in relation to fertilization:
Light greenish, brown-green or greenish
water is most suitable for fish culture.
Dark brown and dark green are not good for the fish

16. BMPs on fertilization and water quality
pH: Best is from 6 to 8 (on a scale of 1-14)
Ammonia: Ammonia exists in two forms
 Un-ionized (NH3) , which is highly toxic to fish
 Ionized (NH4), which is less toxic to fish

17. BMPs on fertilization and water quality
Measuring water quality parameters
It is a good practice to measure
water quality parameters because the
measurements will help you to decide
whether or not to fertilize your ponds

18. BMPs for water quality
Observation Possible measures to mitigate problems
High temperature (>30 °C)  Exchange water (water going in and
out of the pond)
Low dissolved oxygen (<5
mg/L)
 Increase water exchange (more water
going in and out of the pond)
 Stop feeding until corrected
 Aerate the water. Moving water
increases DO
 Stop manuring your pond

19. BMPs for water quality
Observation Possible measures to mitigate problems
High ammonia
(>0.25mg/L) or pH higher
than 9
 Exchange water (water going in and
out of the pond)
 Reduce feeding rate
 Watch for symptoms of
parasites/disease
Low pH (<6)  Add alkaline buffer (lime/ash)

20. BMPs for water quality
Observation Possible measures to mitigate
problems
Transparency too low (<30
cm)
 Exchange water in and out
 Stop manuring the pond
 Stop feeding
Transparency too high (>45
cm)
 Do not let water in the pond
 Add more manure to your pond
 Give supplementary feed
Dark/ deep green  Exchange water in and out
 Reduce feeding rate
 Stop fertilizing

21. Fish Health
Common clinical signs of diseases and parasite infections in tilapia:
 Fish reduce or stop feeding
 Lesions or hemorrhages (blood) on the body surface or eyes
 Tail and fins start to rot
 Gills become pale and damaged
 Cotton-wool like fungi observed on fish body
 White spots observed on the body and fins
 Black and white spots or cysts present on the gills

22. Fish Health
 Reduced growth rate
 Physical weakness and fatigue in movement
 Fish swimming in circles, losing balance, floating upside down
 Reddish pigmentation around the anus or on the genital papilla
 Cloudy and opaque eye
 Bloated belly or dropsy condition
 Swelling of internal organs, such as liver, kidney, gall bladder and spleen.
 Hemorrhages on internal organs
 White or black nodules or cysts on internal organs

23. and notfeeding
Finrot/tailrot
beststepstomanageaquaticanimaldiseases.Ifyouobserveclinicalsigns,abnormalbehaviourandunusualmortality,
contact your local aquaculture health professionals to report and ask for support.
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24. BMPs on fish health
Do not stress fish  Minimize stress by using the right stocking density
 Regularly feed the fish
 Handle fish only when necessary and do so carefully
without removing their scales
 Maintain good water quality by applying correct manure
application rates
Sample your fish regularly  Check a sample of your fish (20-40 fish) for growth and
health once or twice a month
 Sample fish in the morning, weigh them as soon as they
are caught and release them back promptly to the pond
 Use sampled fish average weight to estimate biomass
and calculate the feed quantity
 DO NOT feed fish before sampling
Observe fish regularly  Regularly check fish for signs of diseases
 A healthy fish has a good appetite and is an active
swimmer

25. BMPs on fish health
Keep farm records  Record daily mortality if observed from pond dyke
 Also record possible causes
 Contact authorities (DoF, Livestock/vet, camp officers, etc.)
as soon as possible in case of disease outbreak or unusual
mortalities on your farm
Quarantine the pond
immediately in case of a disease
outbreak
 Make sure no people enter the pond except authorized
persons if necessary. Disinfect equipment such as nets,
hapas, etc.

26. BMPs on fish health
To
Properly dispose of dead fish  Remove dead fish from the pond as soon as possible
 Dispose dead fish far from the pond by burying or
incinerate (burn) the dead fish
Implement farm level
biosecurity protocols
 Make sure no animals, people, vehicles enter the
farm/pond without appropriate disinfection
 DO NOT use farm equipment from other farms without
appropriate disinfection
 Quarantine fish from other sources including from wild
 Quarantined diseased fish
Avoid construction of rosary
ponds
 Construct ponds with independent water inlets and
outlets to avoid spread of diseases from one pond to the
other

27. Thank you