Get the most from your fish pond

Every living thing must have food to be able to grow. Let’s think about the kinds of food that fish eat from the time they are very tiny until they are big enough for people to eat.

Fish that live in streams and lakes grow very well, but sometimes fish that live in ponds don’t grow well at all. In some cases, fish such as tilapia or carp in a fish pond may not be any longer than five centimetres (two inches) when they’re a year old! One reason is that there just isn’t enough of the kind of food they need in that pond.

Many people don’t realize that with plenty of food that costs little or no money, those fish could weigh as much as 25 grams (half a pound) in six months! So if you keep fish in a pond for food for your family, be sure that there’s always plenty of fish food in the pond.

What kinds of food do fish need to grow well? Fish really like insects, insect larvae, things like that. They also like a kind of natural growing fish food that makes the water look different when there’s a lot of it. This food is called plankton and it’s actually a lot of very tiny forms of life that grow in the water.

Let’s think more about that later. But first, I’ll tell you about a simple method that farmers in Thailand use to provide insect larvae for their fish. They build small bamboo platforms about one metre (three feet) square just above the water in several places around the pond. They mix up some pig manure with some compost and place it on the platforms. Flies then come and lay their eggs in the manure. Soon there are lots of larvae falling through the spaces between the bamboo right into the water; perfect food for the fish! From time to time, of course, the Thai farmers replace the fresh pig manure, so more flies will lay more eggs and produce more larvae for the fish.

The other kind of fish food I mentioned a few moments ago is quite different. You don’t actually put it in the water because it grows itself and the fish eat it. To get this special fish food growing, you have to fertilize the pond, something like the way you fertilize the soil to make your plants grow better. And how do we normally fertilize our soil for little or no cost? One way is by applying manure or compost. Well, you can also fertilize a pond by doing the same thing.

Near Chiang Mai in Thailand, George Atkins visited the Centre for the Uplift of Hilltribe Farmers, where Rupert Nelson showed him four different methods they use to fertilize their fish ponds. Across a corner of one pond, there’s a short fence right in the water that encloses a triangular area about two metres (six feet) each way. The fence is made of wooden stakes close together driven into the ground in the bottom of the pond. Into this little fenced- off area, they throw any old plant material, weeds, grass, straw, leaves, kitchen wastes, and even dry cow or buffalo dung, anything that will rot down there in the water.

At one end of another pond, a pig pen has been built out over the water. This is so the pig manure can be scraped from the floor right into the pond. Then too there’s a building where rabbits are kept. It’s also built over the water so the rabbit droppings can go into the water to help fertilize it.

And finally, there’s a goose pen with a slatted floor so the goose droppings will fall directly into the water. By the way, Rupert Nelson says that another advantage of raising geese over the pond is that the geese help protect the fish from being stolen as they make a lot of noise whenever strangers come near.

So there are four good sources of fertilizer for a pond that really don’t cost any money. And it doesn’t take any special work to get the fertilizer into the water.

What does this fertilizer actually do in the water? It makes it possible for those very tiny forms of life, the plankton, to grow. And the more fertilizer there is in the water, the more plankton will grow, and the more fish you can keep in that pond.

Some people believe that water in a pond where they raise fish, tilapia, or carp, for example, should be so clear you can see the fish down in the water. That’s not correct. Clear water doesn’t have much plankton in it. In fact, Rupert Nelson says, ponds that produce the most fish don’t have clear water at all because there’s so much of this natural fish food in them. He described a very simple way to tell when there’s enough of this kind of food in the water.

He says to put your arm straight down into the water as far as your elbow. If you can see your fingers down there in the water you should be fertilizing it more. But when there’s just the right amount of fertilizer to grow the right amount of plankton for the fish in your pond, you’ll hardly be able to see your fingers. So there’s your way of knowing how much to fertilize your pond for the most efficient production of fish.

Notes

1. Another DCFRN item on feeding fish in a fish pond supplements this information very well. Consider using it with the first part of this item.

Feeding fish in your fish pond – Package 6, Item 1/D

2. Other items that might be applicable are:

Food for your whole family from a small fish pond – Package 1, Item 5

Raising fish in the paddy field (Part 1 – Why and How) – Package 14, Item 13