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©Copyright 2015
R&D AquaFarms Inc.
Oshkosh, WI 54904

   

Helpful Tips and Information About
Aquaculture and Tilapia

 

What do you need before you get fish?

A place to put them is the best start. Recirculating systems are most common for tilapia production. Commercial systems are available from a number of sources (see listings in the links section). A system may also be designed and put together on your own. The book Small Scale Aquaculture by Steven D. Van Gorder is one example. There are also plans for aquaponic systems available. Systems can range from $200 for a small do-it-yourself system to $3000 for a complete commercial system.

A reliable heater is a must for tilapia production.

Water test equipment or test kits are needed to check water quality on an ongoing basis. See the water testing section for what kits may be needed.

Proper feed for the fish is important to fish growth. While tilapia aren't fussy eaters, food with a protein content of 35% to 45% will ensure good growth. We keep a few sizes on hand, a small size for fish up to about 6" and a larger size for bigger fish. If feeding fry (less than about 1-1/2") the smaller food can be ground with a coffee grinder or pepper mill before feeding or use our fry powder.

If you prefer, you can prepare your own fry food by using the following recipe.

  • Soften 1 quart of dry fish food in water
  • Mix 2 eggs into food
  • Boil 2 cups of water and add 1 ounce of Knox gelatin, sir until disolved
  • Mix gelatin with egg/food mixture, an old food processor or blender works well
  • Recipe can be cut in half. Store in refrigerator!

If stocking a few small fish in a new system not much needs to be done before the fish are added. Be sure that the water is at a stable safe temperature and that water parameters are within the safe limits. If you are adding a larger load of fish to a new system it may be wise to get the biofilter started before the fish are added. To do this you add small amounts of ammonia to the tank and monitor the water quality levels. Start by adding non-detergent household ammonia or ammonium-phosphate fertilizer to the tank to bring the ammonia levels up to about 3ppm; add a few tablespoons at a time to reach this point. You can also add biofilter starter bacteria if preferred. Test the water for ammonia every few days and keep the level at 3ppm for a few weeks. After 1 week start testing for nitrite; you should see nitrite levels increasing over the period of another week and then start to drop. A few days after the nitrite levels start to drop, stop adding ammonia. When the ammonia levels drop to less than 0.5mg/L it will be safe to add fish.

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Unpacking Your Fish

When adding fish to any system stress can be one of the biggest problem. To keep their stress low you must allow them time to adjust to the new water.

  1. Take the bag of fish and without opening it float it in the tank for a minimum of 15 minutes.
  2. Open the bag and roll down the top edge of the bag two or three turns. This will help the bag float with the opening up. You can put a small airstone in the bag at this point if you have one.
  3. Now add water from the tank to the open bag. Over the next 10 to 15 minutes add one to two gallons of tank water to the bag.
  4. Put the fish into the new tank by grabbing the bottom of the bag and turning the bag upside down.

The fish will take a while to get use to the new tank but should take food in a few hours. Feed them slowly at first watching to see that they eat all that is offered.

If the fish are smaller than your pump intakes or outlets please see Little Fish in a Big Sea.
Some tilapia like to jump out of tanks. To be safe you can put bird netting over the tanks to keep the adventuresome ones in the water.

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Little Fish in a Big Sea

Putting small fry into a large recirculating system can cause many problems. Fish can be sucked into intakes or swim though outlets, feeding can be difficult to control and checking on fish health and loss can be impossible if you can't find them.

To solve this make a small tank inside your larger tank. Using a 5 gal. bucket cut two holes out of the sides. The holes should be about 6" wide by 3" high on opposite sides of the bucket. Make one of the holes about 2" from the bottom and one about 4" from the top. Cover the holes with fiberglass window screen. The screen can be held on with hot melt glue or silicone caulk. If you use caulk check that it is safe for fish use. To help the glue or caulk stick better you should rough up the inside of the bucket with coarse sandpaper. The caulk can be spread smooth with one of the pieces of bucket that you removed.

The bucket is then placed in the larger tank and held in place by the handle with wire or some sort of tie. Place a few rocks into the bucket to keep it from floating. The top edge of the bucket must be above the surface of the water.

Now you have a small tank that you can use to keep track of new fish.

R&D AquaFarms also has an advanced version of these buckets available for sale. Contact us of more information.

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Feeding

The growth rate of tilapia is controlled by water quality. temperature and feeding rates. If the water is correct tilapia like to eat more than almost anything else. Feeding four or five times a day is best as the tilapia digestive system runs on a two to three hour schedule. A basis for how much to feed can be calculated from the chart below.

Let's say you have about 100 fish that weigh 35 grams each. Your tank will have 3500 grams of fish to be fed. From the chart you can see that 35 gram fish should be fed about 4% - 7% of their body weight per day. We'll take 5.5% for this example because the 35 gram fish are in the middle of the weight range on the chart. 5.5% of the 3500 grams of fish we have is 192.5 grams of food. We can then split the 192.5 grams of food in fourths to make the four feedings for the day.

If you are checking fish weight on a weekly basis, you can do the calculation each time you check fish growth and up the feed amount each week. If you're not you can calculate the new fish weight by taking the weight of food you have fed in one week times 0.75. In our example this would be 192.5 grams x 7 days = 1347.5. Take 75% of this, 1010.6 grams (the 75% allows for the food conversion rate for tilapia). We’ll round this to 1000 grams. You then add the 1000 grams to the original weight of the fish at the start of last week 3500 + 1000 = 4500. This will be the new total weight of the fish in the tank. Now you should have 100 fish totaling close to 4500 grams, at 45 grams per fish. Look this up in the chart and calculate the new feeding rate for this week. We'll say 4.5% or 4500 grams = 202.5 grams per day.

The feeding rates are only a guide but will help you determine if your system is operating correctly.

If at any time things seem to go wrong the first thing to do is to stop all feeding and determine the problem. Watch closely for the first few days to be sure all food is eaten at each feeding. Also watch ammonia levels and stop or reduce feeding if they rise above caution levels. It can take several weeks for a clean tank and filter to start working properly.

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Water Testing

It is wise to have water testing equipment or a water test kit available. Water testing should be done on a regular basis and the results tracked to look for changes. Slowly changing parameters will not affect the fish until dangerous levels are reached, but quickly changing parameters can immediately affect fish health. In testing with a test kit be sure to keep the test tubes clean and never put water from the test back into the tanks.

At the very minimum you should have test equipment or test kits available for the following parameters:

  • Ammonia
  • Dissolved Oxygen
  • pH, Nitrate
  • Nitrite
  • Temperature

Other tests that you may need include:

  • Chlorine (if you use city water)
  • Alkalinity
  • Carbon Dioxide
  • Hardness

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