The need for predators in tilapia farming

For some this may make no sense as to why one would want something to eat their fish, if they are trying to grow and raise them. I felt exactly the same way at first.

When you purchase your tilapia, the majority, and I am talking about 98-99% here will be male. The reason for this is they are given a hormone at the start of their life which can alter their sex. 1-2% doesn't seem like a lot of females but when you realize the amount of eggs a female can produce, and many of those will be females. you can see how the problem can escalate.

There are several reasons why you don't want breeding to occur. The first is you will have a population explosion. These fish will all be competing for food. As such none will grow to the intended size you had hoped for.

The second problem will be as the fish are breeding, they make holes (nests) along the edge and bottom. This will result in an uneven bottom making netting much more difficult. When the time comes to net the lake, the fish will be able to escape below the net using one of these holes.

Another problem which we were unaware of at first was the behavior of the fish. We netted some larger fish and put them in our tanks waiting for them to sell the following weekend. It was here where we saw behavior which would also be occurring in the lake, although unseen.

In tanks with a female, she would stay in a corner guarded by a male. The other fish would hover around waiting for their chance to be 'top male'. They were so interested in her, they weren't eating. Tilapia which aren't eating aren't gaining weight and aren't going to earn you money.

It is for the above reasons why you need predators if you have your fish swimming freely and don't sell all of them before breeding begins, which can be as early as 4 months

The cost of electricity

For many people this could be the making or breaking of a profitable tilapia business. The cost of your electricity is something which needs to be taken into consideration before embarking into the fish business.

The electricity usage would come from a few different avenues.

• Aeration
• heating of water
• water pumps
• security lighting

The aeration, if you are using, can be costly and this would have to be weighed off against the increase in the number of fish you can rear with using it. Some people we know only used their aeration systems over night. We used ours 24/7.

The heating of the water is something you may have to consider depending on where you live. This isn't always necessary as tilapia are hardy fish and can take temperatures as low as 45ºF (7ºC). Although that means your fish might survive it doesn't mean they will thrive. Remember you are in this business to make money and that means you want to spend as little as possible to make maximum profit. If your fish are using their energy (provided by the food you are feeding them) to keep warm, they aren't using those calories to grow.

Water which is naturally warmed by the sun is best for your pocket.

This is one of the reasons why Brazil, where I live, is perfect for raising tilapia, we never have to heat the water.

In saying that, if we were pumping straight out of the ground into tanks, it is cooler and would affect production and profitability.

That brings me to the next item on the list. If you are moving water from one lake to another or continually adding fresh water you will be using some sort of pump. There are many types available. To know which is best for your set up, it is worth speaking to an adviser who sells them. They will be able to tell you the volume of water each pump can move through the various pipes. This is also dependent on the depth of your well. 

 

Security lighting around your farm is necessary. You have a valuable and easily removable crop and lights are necessary. There is also the added benefit that these lights attract insects which fall into the water. An additional ( and free) protein source for your fish. 

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. 

How to build duckweed ponds

Here on our farm we built 5 duckweed ponds after reading about this fabulous plant. We had not seen this plant growing locally but luckily a friend of ours, found some in a pond in the mountains near here. He brought us two types, on with smaller leaves and one with larger. He was studing botany and told us the smaller leaf variety did better in a shady spot and he was right as our ponds were in the full glare of the sun and it was the larger leafed variety which grew well in our conditions.

View across duckweed ponds

We hired a backhoe and a driver to dig our lakes which were 30 m long by 2 m wide (98' x 6.5'). We then put clay down and lined them with a plastic liner. These are shallow, only about 2' deep.

Clay lined duckweed pond

 As you can see these take a bit of organising but in the end, they aren't that difficult to create. If you were to build them there are a few things to keep in mind.
The liner is crucial. Here we had to take several things into consideration.

• Ability to cope in extreme UV conditions. (we have over 300 days of sun a year and more often than not our level of UV (Ultraviolet light) is in the extreme category. Your local weather forecast can help you determine what your UV index is for your area. 
• Non-leaching. We had to make sure that no toxic or unpleasant chemicals would leach into the water which could cause problems for the duckweed and subsequently the fish.
• Robust. We had to have a strong plastic liner. Often bits of twigs might end up in there. Also we have chickens. We needed something that was tough enough to resist being damaged.

Various stage of completion

We first lined ours with clay as you can see in the pictures. This was delivered and we spread it manually and flattened it down to prevent any pebbles from damaging the liner. The reason we used clay is if any water were to seep out from the liner, it would be a slow leak. We have sandy soil here and it sucks up water better than a sponge, hence our need for clay.

Overflow system for duckweed ponds

Because this was only designed by us, we had to solve problems as we went. What you see pictured above is the ingenious (and cheap) solution my husband came up with. The problem was, we needed an overflow system for water to run out if the ponds got too full. We can get heavy downpours in our wet season which would have sent our duckweed up and over the edge in a rainstorm. We could have lost it all if that happened. Remember, duckweed is a floating plant, it isn't rooted into anything.

My husband place plastic pipes from one lake to the other. Then to keep the duckweed in and allow the water to flow out, he simply cut the bottom off a 2 liter soft drink bottle and insert this onto the plastic pipe. The excess water would escape and the duckweed would stay in the pond.  Sometimes the solutions to problems are easier than we think.

We started these ponds with just a few duckweed plants and yet you can see how quickly and how full they became. It can double itself in about 16 hours!

Feeding your Duckweed Pond
You will need to help your duckweed to grow by adding manure. We used chicken manure which a friend of ours sells. He buys it in from a factory farm and it is extemely strong. My husband would half fill a plastic trash can with manure and add water to soften it. This he would then throw into the duckweed ponds with a bucket. This ensured it was spread throughout the pond. If you have put enough manure in, you will see a growth spurt. If you don't, look at the roots of the duckweed plant to see how long they are. If they are long, perhaps more than 2 inches, you need more manure. Duckweed loves mucky water. Infact there are countries, Palestine for example, which use duckweed to clean their water supply. It is one plant which has so many uses. For more information about some of the other uses, I have written another article on Hubpages.
 http://blond-logic.hubpages.com/hub/duckweed

Cleaning your duckweed pond

I know what you are thinking, that this is going to be difficult but it isn't and it is necessary from time to time. If your duckweed seems to be slowing down with its reproduction it might be time to change the water and start again. We had to do this when we had a build up of sawdust in our ponds. This came in with the manure as this is what was used on the floor where the chickens were kept.
There are a couple of ways to do this, either let the water evaporate or drain it with a bilge pump, or a siphon. If you are going to be siphoning this, using your mouth to start the flow of water, remember how much manure you have been putting in there.

Remember keep some duckweed as a starter  

This starter can be kept alive in water until your pond is ready to go again. Once dry, sweep and remove any twigs, leaves or other debris from your pond. This is a good time to inspect your liner below the water line.

Havesting your duckweed

Harvesting is easy. We used a swimming pool net on an extendable aluminum pole. We briefly let the water drain from the net and then turned the duckweed into a large plastic box. We filled this full. This was then loaded onto our kayak  to take to the tilapia which we had transfered to cages.
Because we were harvesting every other day we were able to check the liner for any problems above the water line as a matter of course. A quick once over as we were scooping it out meant any problems were dealt with early and were thus easier to control.

Cost vs Savings

The cost for us was perhaps more than it would be for yourselves as we had to hire a machine to dig the holes for us. But compare this to the savings. If you calculate that your fish are only eating commercial fish food every other day, you have halved your food bill. If you only have a small number of fish, maybe this isn't commercially viable. We had bought 10,000 and had it definitely made financial sense to do this.
We produce healthy, weighty fish at half the cost of other fish farmers in this area.