Do you know how much water is in your pond? How accurate are you? If you used a flow meter while filling the pond, chances are you do know the exact volume. But if you are estimating, you may not be close enough. Why you ask? Well, I'll tell you! lol!

The most important reason for knowing how much water is in your pond is if you ever need to dose your pond with medication for sick fish. Some medications are pretty forgiving and an overdose won't hurt anything. But some are not. Some medication will kill your fish if you overdose, and will not kill the parasites if you under dose. So sometime this summer, you should spend a little time doing this "salt volume calculation" so that you will be prepared if your fish ever do get sick. The amount of salt required is not enough to hurt most plants, so don't worry about that. This all sounds complicated, but really it's not. OK...ready?

10 pounds of salt increases the salt level of 1000 USA gallons by 0.12%

One pound of salt per hundred gallons equates to a salinity of 1.25 ppt (0.125% or 1250 ppm). With a digital salinity meter, there is no need to crank the salinity above 0.15%, which is a still a safe level for adding therepautic meds. (Salt is a poor pond treatment for parasites anyway.) You can also use a salinity test kit which is available from any store that sells salt water fish tank supplies.

Test the salt levels before you begin. For example, lets say your test says your initial salinity is 0.03%.

You think your pond is 1000 gallons, and you want to raise the percentage an additional 0.125%. Since one pound of salt per 100 gallons raises the salinity up by .125% and your pond is 1000 gallons, you will want to add 10 pounds of salt (be pretty accurate on weighing the salt or it will throw the calculations off). So now your salt levels should be .155% (because of the initial salt, and the added salt).

So you test your water again, and the salt levels are not .155% as you expected, they are .2%!!! So what does that mean? It means your pond does not hold 1000 gallons, or it would not be so salty. So how do we calculate how much it really holds? We calculate the change in salinity by subtracting the initial salinity from the final salinity..so .2% - .03% = 0.17%.

Volume = (pounds of salt added / the change in salinity) * 12.5 (this 12.5 is a mathematical constant and never changes for this exercise)

(10/.17) * 12.5 = 735 gallons. Instead of the 1000 gallons we thought we had, we only have 735 gallons.

Another example........

Pond estimated at 2500 gallons.

salt added = 20 lbs lbs salt

initial salinity = 0.03%

final salinty = 0.16%

change in salinty = 0.13

here's the math: (20/.13)* 12.5 = 1923 gallons

calculated pond volume 1,923 gallons.

In a nutshell, adding 20 pounds of salt to a supposed 2500 gallon pond let us know that the actual volume was only 1923 gallons.

See? That was easy! These calculations are not 100% accurate, but they are accurate enough to dose your pond with chemicals.

Have fun!!

Cindy