Chemicals

Chemicals should be used in fish culture only when there is no alternative. Ponds can require chemical treatment for:

Not all agricultural chemicals are approved for use in food fish ponds. Check with your county Extension fisheries specialist for the latest recommendations.

When chemical treatment is prescribed, how do you calculate the amount of chemical needed to get the required concentration? Before treating any body of water, you must consider these things.

The Fish

What are the tolerable limits of the fish to the chemical?

The Water

In the pond to be treated, what water quality factors will affect the chemical being used? Could hardness or muddiness increase the toxicity of, or render ineffective, the chemicals beings used?

The Chemical

What percentage of active ingredient is in the chemical formulation?

The Pond Size

What is the exact volume of water to be treated? Many fish have been killed because pond volumes have been exaggerated. Overestimating the pond size will cause an overdose and probably kill fish. On the other hand, underestimating the size may result in an ineffective treatment.

Know the volume of your tanks and ponds. Keep a record of this volume for future treatments.

To calculate the volume of a square or rectangular body of water, multiply length times width times average depth of water. This will give you cubic measurement of volume. Cubic feet (ft3) and acre-feet are the measurement most commonly used. The area and volume of irregularly shaped ponds are much more difficult to determine.

The local SCS office can assist you in determining surface area and possibly average depth. Average depth can be estimated by multiplying the maximum depth by 0.4. Remember to use the same units of measure for each body of water to be treated.

One very accurate way to measure pond volume is through the use of chloride tests.

  1. Take water sample from the pond and test it for chloride (ppm). Reserve this sample so it can be compared to later samples.
  2. Broadcast 50 pounds of salt per surface acre of the pond. The total pounds of salt added must be known, but he pond acreage can be estimated.
  3. Allow the salt to dissolve. Usually one day is sufficient.
  4. Take several water samples from different areas and depths of the pond. Test these new samples for chloride concentration.
  5. Calculate the average chloride concentration. Add the chloride concentrations of all the samples together. Divide by the number of samples.
  6. Calculate the change in chloride concentration. Subtract the beginning chloride concentration (the concentration of very first sample) from the average chloride concentration.
  7. Calculate the pond volume using this formula:

 Volume (in acre-feet) =

  (weight of salt applied x 0.6) /2.71 change in chloride concentration (ppm)

Measure accurately! Since 1 acre-foot of water weighs 2.7 million pounds, then 2.7 (2.71 in the formula above) pounds of any material (or active ingredient) dissolved in 1 acre-foot of water gives a solution of 1 part per million (1 ppm). This method will not work in hill-type ponds that are stratified.

The volume of water in watershed ponds may vary considerably from month to month. A producer should know the volume of ponds at different pond depths, so that chemical can be applied correctly. Remember, low estimates may result in ineffective treatments and high estimates may cause overdoses and fish kills.

Table 9 shows the weights of chemicals that must be added to 1 unit volume of water to get a concentration of 1 ppm.

Table 9. Chemical Active Ingredients Needed To Produce 1 ppm Concentrations.

 Amount Active Ingredients

 Unit of Volume

Parts Per Million

 2.7 pounds

acre-foot

1 ppm

 1,235 grams

 acre-foot

 1 ppm

 1.24 kilograms

 acre-foot

 1 ppm

 0.0283 grams

cubic foot

 1 ppm

 1 milligram

liter

 1 ppm

 8.34 pounds

million gallons

 1 ppm

 0.0038 grams

gallon

 1 ppm

Table 10 contains conversions that are helpful in calculating treatments. More conversions to assist in chemical treatments can be found in Extension circular ANR-414, "Tables For Applying Common Fishpond Chemical," available from your county Extension agent or the Extension fisheries specialists.

Table 10. Conversions For Treatment Calculations.
 1 acre-foot
= 1 surface acre of water 1 foot deep
= 43,560 cubic feet
= 2,718,000 pounds of water
= 326,000 gallons of water
1 cubic foot
= 7.5 gallons
= 62.4 pounds of water
= 28,355 grams of water
 1 gallon
= 8.34 pounds of water
= 3,800 cubic centimeters of water
= 3,800 grams of water
1 quart
= 950 cubic centimeters of water
= 950 grams of water
1 pint
= 475 cubic centimeters of water
= 475 grams of water
1 cup
= 240 grams of water
1 tablespoon
= 14.8 grams of water
1 teaspoon
= 4.9 grams of water
1 pound
= 454 grams of water
= 16 ounces of water
1 ounce
= 28.35 grams of water
 1 liter
= 1,000 grams of water

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