Tilapia cages. What makes a good one?

Although you may have heard that the tilapia can be successfully reared in a cage, you may not have realized just what is needed. There are some I have seen on sites such as Ebay. These are a thin netting material with floats. Often these will be for very young fish as the material is not robust enough for adult fish. A cage in many ways is preferred to rearing in a tank because the fish waste drops through the cage to the bottom of your lake or river.

Here on our farm we have used a few different types, some are better than others for various reasons. Here are a few things to consider.

The frame. What material is the frame made of? This could be aluminum, wood or plastic pipe. Each has its advantages and disadvantages.

material	Pros	Cons
Plastic pipe	Lightweight, inexpensive and readily available, easy to fix	May deteriorate in the sun
Aluminum	Lightweight, doesn't rust	Needs to be a good quality otherwise will bend with weight of fish
Wood	We used Hardwood which lasts	Can be heavy to lift, out of the water could be prone to insects.

Besides the frame which will hold the netting or the structure of the cage. For this we have used two types. One was a heavy duty plastic, the other was plastic coated metal. Similar to a chain link fence.

Over time both of these needed repairing as areas would become holed and allow fish to escape.

Every time the cages came out of the water for the fish to be sold, they get cleaned and thoroughly checked for potential problems. The plastic ones we repair with strong cord, and the metal ones we use coated wire to patch up areas.

You also need a way of making the cages float as you do not want the cages sitting on the bottom of your body of water. We use plastic cans which in their previous lives were used for cleaning products. These were perfect but after two years in the Brazilian sun, needed replacing as they became brittle and would crack and take on water.

This is why, during feeding time, it is always a good idea to do a quick visual scan of the cages to preempt any potential problems. Keep extra buoyancy aids in a covered area. It would be a shame to see all the fish in your cage escape due to a listing cage.

We had a local welder construct small cages to hold the containers in place. These simply hooked over near a corner. On our 2m x2m cages we use 4 floats. On our 2m x 3m we use 6 floats.

As well as the frame, the cage material, and the floats you will also need to put fabric mesh around the top edge of the cage. Ours was about 18” wide. At first this doesn't seem necessary but when you feed the fish in the cage, this mesh will keep the food from floating out of the cage and being wasted. This should be tied onto the cage to keep it from floating up, which trust me, is a nightmare.

The last item you will need is plastic mesh for the top of your cage. This serves a couple different purposes. One is to keep the fish in the cage. Although you may think that tilapia don't jump, they will. With a cage which is just floating above the height of the water, they will be out in a shot. The second reason is to keep out birds. We have had herons, egrets and moorhens all sitting on our cages. The herons and egrets are trying for the fish and the moorhen is eating the fish food.

Cages for fish rearing

Here on our tilapia farm we have three different types of cages. There are several materials which you can use to make the structure with and also those which form the netting of the cage itself. You can buy them ready made on places such as Ebay or you can make them yourself.

We bought ours used, and did a few repairs to them to get them ready for the fish.

Our cages which are 3m x 2m are on aluminum frames and the cage itself is plastic coated wire. This has advantages and disadvantages. The advantage is it is lightweight. When you are moving or lifting it , once filled with fish any extra weight just makes your job more difficult.

The metal cages could take fish beginning at 50grams, any smaller and they could swim out through the space between the chainlink.

tilapia cage

The other type we have is heavy duty plastic on a wooden frame. These are 2m x2m and are heavy.This is due mainly to the frame as all the wood here in Brazil is hardwood. Yes the wood will last virtually forever but it is heavy. The plastic netting is very strong and the gaps are smaller which allowed us to buy smaller (less expensive) fish. When using the plastic cages, we could buy fish which were 30grams.

The third type which we bought, we didn't use as, although it was lightweight, it was cumbersome. This was made out of pvc pipe and was rigid.

The truth is you can make the size you want or need using most anything.

The 3m x2m has the capacity to hold 900 fish and the 2m x2m can hold 600. We always kept the amount less than this as we didn't want to stress the fish.

To keep it afloat we had a welder make small baskets into which we put empty plastic bottles. These had originally held industrial cleaning products but once empty were sold off for various uses. If you use this idea, be aware that after a time in the sun, the plastic does become brittle. It is always a good idea to have spares around, otherwise your fish could escape as the cage would sink on the side where your container has filled with water.

It is also necessary to have a lid on your cage for a couple reasons.

1. Fish can jump out.
2. To keep fish eating birds out. This includes herons, egrets, cormorants etc
3. To keep birds from eating the fish food.

Along the top edge of the cage you will also need to put a fine mesh. This should be tied down to the cage. This keeps the fish food from floating out before the fish eat it. 

Sometimes you may notice the tilapia have red or bleeding mouths when raised in a cage. This is from hitting the side of the cage, trying to get out. This however never affected resale value as we sold by the kilo.