Figure 7. Fish Pond for the Micro Farm.
Of the entire microfarm, the fish pond is perhaps the most difficult part to accomplish. This pond is designed to be 10 by 50m and it should grow out 2400 fish a year. That is 4.8 kg/mē in production.
The fish we will grow is tilapia, probably a cross between nile and java tilapia. The fish should reach 1 kg in weight after 1 year in the grow out pond.
200 fish are available for harvest each month. 200 kg of protein for consumption or sale each month. It is estimated that 10kg of this will be eaten by the family and 190kg sold.
The fish pond requires a clear water tank for fish about to be harvested. Clear water makes the fish taste better, they need to be in this tank about a week, so it should be at least 25m3 for 100 fish.
There also needs to be a brood tank for young fish rearing during the year. Requiring an estimated 500 juveniles a month. This should be 10 females and 5 males, this can be 25m3 tank again
The sierra micro farm has a 500 meter fish pond. This pond is one meter deep so it contains 500 cubic meters of water.
The stocking level of tilapia grown in the pond is 4.8 per cubic meter, so it grows 2400 fish.
The pond is fertilized with nitrogen (18 kg N year and 2.56 P) and the fish are also fed 1200 kg worms during the year. They are expected to require no other foods.
Each day the corn field is watered with water from the fish pond. The 1200m cornfield is expected to require 2400 liters a day.
The possible draw from fish pond is 50,000 liters a day, 10% of the water volume, allowing that much fresh water. It is enough to water the blackberries and the legume field.
The 4800 fish probably eat 3% of body weight a day, and excrete 25% as waste. Assuming all wastes are in water, they excrete an average of 36kg waste per day, only 3% nitrogen.
The nitrogen for fish is in food and algae grown in the pond.
The pond is a safety halard for small children and should be fenced with a spring latch gate.
Pond is built of excavated earth build up around sides. Bulldozing is reccomended to build pond.Table 1. Model results for Pond (OSU) show it takes 20 months to produce a 800 gram fish.
Revised: 15 December 2007
Copyright © 2007 Microfarms, Inc