Update on High density fish farming (Re-circulating Aquaculture

System) experiment at Vigyan ashram.

We are working on HD fish farming by adopting RAS system. The trial is started the

month of January (2015 with system consisting of Fish tank (Tillapia fish), Bio-filtration

bed, Water circulation system (details can be found on-

https://vigyanashram.wordpress.com/2015/02/15/recirculating-aquaculture-system-ras-

trials-started-at-vigyan-ashram/)

The experiment update is as follow-

1. Fish Growth & FCR-

Fish growth rate is measured by random sampling with 15 days interval.

So far for 2 sampling in last 1.5 month we received 3.4 % average FCR with

average fish wt of 34.57 Gm and total tank density of 232.8 Gm / M3.

FCR is pretty high at the point and we are trying and we are expecting to reduce

it to 1.5 % for next 4-6 and hope to raise fish density up to 8 to 9 Kg / M3.

Feeding rate is maintained @ 7 – 5 % of body Wt.

Feed prepared by using race bran + GOC and soy chunks containing 45 to 48 %

protein.

Feeding frequency is maintained @ 3 Hr during day time.

Meanwhile we have also started harvesting Spinach @ 2.5 KG / week from Bio-

filter.

(Details on feeding rate, Fish feed formulation and FCR calculation are given in

Annexure I )

2. Water circulation and Water Quality Parameters-

Water height in fish tank is maintained @ 0.9 M comprising total tank volume of

around 51000 lit.

Water circulation system is operated to keep DO level around 7 – 10 PPM and

NH3 level below 5 PPM.

Screen filter is added in system to clean fish tank water and avoid micro-sprinkler

clogging.

Work on developing handy NH3 testing kit for HD fish farming also started.

During fish sampling this is found that bottom layer water in fish tank ( 1 to 1.5 Ft

) is developing anaerobic growth due to heavy accumulation of fish water and

feed remaining. This is mainly because we have placed water pump above 1.5 Ft

from bottom of fish tank and there is no provision for removing slump from

bottom of tank.

To overcome this slump problem at present we are using siphon based water

removing system.

Water circulation time is modified from 1 Min / Hr to 0.5 Min / ½ Hr.

With flow rate of 7000 to 10000 Lit / Hr , system water requirement is around

2300 lit / day. The water requirement is high due to high evaporation losses from

Bi-filter and removal of slump through siphon.

3. Important learning’s –

Measuring NH3 levels by developing simple colorimetric chart.

Anaerobic growth in fish tank need to control.

Maintaining proper water circulation rate in bio-filter is important to maintain

water quality parameters.

Feeding frequency is equally important as that of feed quality and rate.

RAS system consisting Bio-filter bed with Spinach and Fish tank

Annexure I –

A. Feeding rate - Daily feeding allowances for different sizes of tilapia fishes :

Size of fish (grams) Amount of daily feed (% of fish weight)

0–1 30–10

1–5 10–6

5–20 6–4

B. Fish Growth Chart

Date of harvesting

No of Fish harvested Total Wt Averag wt

Average length (Cm)

22.02.2015 40 1.011 25.28 12.7

11.03.2015 92 3.18 34.57 11.9

C. FCR Calculation -

Feed Conversion Ratio ( FCR ):

It is an indicator of the:

i. performance of a feed,

ii. ii. performance of the person feeding the fish and the fishes health

iii. iii. Cost-effectiveness of using a particular feed.

The feeding frequency is the number of times fish in a pond are fed in a day. The feeding

frequency affects the efficiency of feed utilization (i.e. the FCR ) so it is important to

establish the optimal frequency of feeding so as to attain the best possible (optimal) FCR

and uniform sizes of fish.

Following are the feeding recent frequency given by us:

To maximize production efficiency and minimize costs, tilapia should be fed .Feeding

Frequency is also one the important factor for growth of fish.

• Nutritionally complete diets.

• Optimum crumbles or pellet size.

• Optimum feeding rate (% of fish body weight).

• Optimum time intervals (4 – 5 hours depending on the energy and composition of the

diet); based on the size of the fish and the culture conditions.

FCR may be calculated as below:

FCR =

D. Fish Feed Formulation -

Fish requires high quality nutritionally balanced diet for growth and attainment of market

size within the shortest possible time. Protein requirements also vary with rearing

environment, water temperature and water quality, as well as the genetic composition and

feeding rates of the fish. Protein required for tilapia fish is about 32-38 %.

Locally produced feed using locally available ingredients will reduce the cost of

production and hence, cheaper fish to meet the protein needs. In Vigyan Ashram we

prepared the fish feed from rice barn + ground nut cake (2:1), as well as soybeans also

used.And the protein content in feed which we prepared is 47.1%.And the cost of fish

feed is 4.26 /-per day.

Report Prepared by –

Miss. Shraddha Rajendra Butte Patil. ( Dr.BSKKV , College of Engineering , 4th

Year

student Intern during in-plant training internship program)