|Better Farming Series 35 - Better Freshwater Fish Farming: Further Improvement (FAO, 1986, 61 p.)|
6. The easiest way to make an even bigger pond is to add a new part to one of your old ponds.
7. You can add a new part to your old pond of 15 x 15 metres. You can make it twice as big. You can make it 15 x 30 metres and still build the banks in the same way that you built them for the old part of the pond.
New outlet and overflow
8. Booklet No. 29, Items 42 to 48, tells you how to make a smaller pond bigger.
9. If you do not want to make your old pond bigger, you can build one or more new ponds of 15 x 15 metres next to your old pond ...
or in another place.
10. You can also build a pond of 20 x 20 metres and still dig the bottom and build the banks in the same way as you did for your old ponds.
11. The top of the banks of a 20 x 20 metre pond should still be 1.50 metres wide as they were with your 15 x 15 metre ponds.
The banks of pond
12. The water should be at least 0.60 metre deep in the shallow part and at least 0.90 metre deep in the deepest part.
Keep the water deep
13. If you want a still bigger pond, you can build one of 20 x 30 metres, 20 x 50 metres or even 30 x 50 metres. The top of the banks of ponds this size should also be 1.50 metres wide but, because these ponds are bigger and deeper and hold much more water, the bottom part of the banks should be stronger than the banks you built for your smaller ponds.
14. Since you will be digging bigger and deeper ponds, you will take out more soil. Put all the soil you dig out on the lower part of the banks. This will make them thicker and stronger.
15. The drawing below will show you what the banks should look like when you are finished.
The banks of a pond
16. However, if you build ponds of this size, you should build them a little deeper. They should be at least 0.75 metre deep in the shallow end and at least 1.00- 1.20 metres deep in the deepest part.
Keep the water deep
17. If you live in a place where the temperature falls below 20°C, make your ponds 1.50- 1.80 metres deep. The water will be warmer in the deepest part and your fish can go there during the colder part of each day.
Remember when ponds are side by side, you will need only one bank between two ponds (see Item 45, Booklet No. 27). If you are building two ponds side by side at the same time, you can make the top of the bank between them 1.00 metre wide instead of 1.50 metres.
One bank between two ponds
18. With bigger ponds or more ponds, you must be sure that you have a supply of baby fish all year round.
19. If you have two or three big ponds that together have an area of more than 500 square metres (one 10 x 10 metre pond + two 15 x 15 metre ponds = 550 square metres), you should have your own nursery pond.
20. If you do not already have a nursery pond, Booklet No. 30, Items 43 to 88, will tell you how to build one, how to care for the baby fish and what to do with them.
A nursery pond
21. If the new ponds that you build are less than 500 square metres (a 20 x 20 metre pond = 400 square metres), you can use pipes with screens for the inlet, outlet and overflow, just as you did in Booklet No. 29 for your 15 x 15 metre ponds.
Inlet pipe with screen
22. For the 15 x 15 metre pond you learned how to build in Booklet No. 29, you made the inlet and the outlet about 10 centimetres in diameter and the overflow about 6 centimetres in diameter. With an inlet or outlet of 10 centimetres, it will take about half a day to fill or empty a pond of this size.
23. If you have built a pond of 20 x 20 metres, your inlet, outlet and overflow should be a little bigger. You can make the inlet and the outlet about 15 centimetres in diameter and the overflow about 10 centimetres in diameter. With an inlet or outlet of 15 centimetres, it will take about one day to fill or empty a pond of this size.
24. You can further improve a pipe outlet by placing a collar of cement around the centre of the pipe.
Collar in centre of pipe
25. The collar will hold the pipe in place in the bank and keep water from seeping through the bank outside the pipe.
26. The drawings below show you how to build a wooden form to make a cement collar.
A collar should be about 10 cm thick and at least 15 cm from the pipe to each edge of the collar
2 build a wooden form to mould the cement around the pipe
3 place the pipe in the form and fill the form with a mixture of one part cement to two parts sand, and some water
4 remove the form after the cement has completely dried
Note: you can make a form using nails; however, if you use wooden screws, you can take the form apart and use it again
27. If the new ponds that you build are more than 500 square metres (a 20 x 30 metre pond = 600 square metres) it will take much too long to fill them using small pipes. You will need better and faster ways.
A trench inlet
28. You can use a trench inlet just like the one on page 30 in Booklet No. 29 to fill a bigger pond quickly. However, you will also need a screen to keep out wild fish.
29. The drawing below shows you a trench inlet with a corrugated metal bottom and a screen made of woven material.
Use corrugated metal
Another kind of inlet
30. You can also build a kind of gate in the trench to control the flow of water into the pond. This is called a sluice.
31. A sluice has a wall on each side of the trench and a floor set into the bottom of the trench. There are slots in the walls to hold wooden boards or a screen.
32. Boards are put into the slots to keep water out of the pond or taken out to let water in. When you are filling the pond, put in a screen to keep out wild fish.
33. You can build a sluice from wood or if you know how to build with bricks or blocks, you can use these.
34. The drawings below and on the next page show you how to build an inlet sluice using wood.
Building a wooden inlet sluice
Parts of a wooden inlet sluice
Where to put an inlet sluice in the pond bank
Another kind of outlet
35. You can build another kind of outlet to empty a bigger pond faster. It is built inside the bank at the deep end of the pond. This kind of outlet is called a monk. When the pond is filled, the monk will be in the water.
A monk is in the water at the deepest part of the pond
36. A monk is a tall box with two sides, a back, a front formed by wooden boards, and a bottom. Each side has two slots to hold two rows of the wooden boards.
37. Boards are put into the slots to keep water In the pond or taken out to let water out. You will learn more about this on pages 20 to 23 of this booklet.
38. A monk also has a screen like the one shown on page 14. The screen fits on top of the first row of boards and keeps your fish from getting out when the pond is too full or when you are emptying it.
39. A monk also serves as an overflow. So, you will not need to have an overflow pipe like the one shown on page 9 of this booklet.
40. You can build a monk from wood, or if you know how to build with bricks or blocks, you can use these.
41. The drawings on the next pages will show you how to build a monk using wood, and how to fill and empty a pond using a monk.
Where to put a monk in the pond
Parts of a wooden monk
Note: the outlet pipe should be placed at the very bottom of the monk
Where to put a monk in the pond
How to fill a pond when you have a monk
1 put both sets of wooden boards in the slots in the monk and put the screen in place on top of the first row of boards
Fill a pond when have a monk
2 the boards should be as high as the water depth that you want in the pond
3 pack the space between them with good clay soil to keep water from leaking out
Keep water from leaking out
4 let water into the pond
Let water into the pond
5 when the water reaches the top of the boards, stop the flow of water
Stop the flow of water
6 leave the screen in place to act as an overflow if the water becomes too high
Leave the screen
note: you may have to let water into your pond from time to time if the water- level gets too low
How to empty a pond when you have a monk
Empty a pond
1 take out the screen and remove the top board from each slot
Remove the top board
2 the water will begin to flow out and wash away the clay that was between the boards
Wash away the clay
3 quickly put back the screen to keep the fish from getting out
Put back the screen
4 water will flow out until it reaches the level of the next row of boards
Water flow out
5 when this happens, take out the screen again, remove the top row of boards and quickly put back the screen
6 more water will flow out
Water flow out
7 continue to take out boards one row at a time, always putting
back the screen, until the pond is empty
Note: later in this booklet, you will learn how to harvest fish when you have a monk