Pond Boss Forums INTRO Questions & Observations Overwintering talpia

I am gon'a to try to keep my talpia alive (here in Central East Texas) this winter by adding well water to my pond.. Whats your thoughts

Where is your place? I am 2 miles north of Brownsboro and my water is about 62 degrees(at 1 foot)right now. We have about 10 more degrees to play with before the Tilapia die-off. I supplemented my pond this year with well water(595' deep) to the tune of about 2-3 foot throughout the drought. I probably added about 750,000 gallons all summer. I'm not convinced it would keep my Tilapia alive..... I lost them last year on December 10th.
Good Luck.

LoopTech,

If I recall the pictures of your pond its a lot larger than 1/4 acre. I think in a very small pond, less than 1/4 acre, it might be possible to keep the water temps above 60 degrees with well water. In a larger pond, I doubt you can add enough well water to be able to keep the temps that high...even at temps in the low 60's however, your fish will be susceptible to disease.

Keep us posted on your experiment...I hope you are successful and if your are, I'll try it myself.

This is the pond I am going to try to Save the Tilipia in.. I think this pond is between a 1/4 and 1/2 acre..

What is your groundwater temperature?

67 deg. My well is 280 ft. deep.. This well was drilled for drilling water, for the gas well on my place. The oil company completed this well with a 5hp pump that delevers approx 100 gallons a minute. I have a 2 inch line from my well to this small pond.

This might not work, but I am going to give it a try..

With an estimate of your pond volume (area X average depth) and the minimum Winter water temp your pond sees, we could estimate how much of a temperature difference 100 gpm of 67 deg F water would make.

If nothing else, this could be roughed out using Cecil Baird's figures for cooling with well water, and checked using straight math.

Average depth 5 ft. X 1/2 acre( probably closer to a 1/3 acre
Not sure about the temp.. But my guess would be 45 degrees

Ok, I'll take a stab at the Math and clearer minds can pick these figures to pieces. I'm using data from How Many Gallons is My Pond?

Worst case, 1/2 acre at 5 feet = 2.5 acre-feet

2.5 acre-feet X 43,560 ft2/acre = 108,900 cubic feet

108,900 ft3 X 7.5 gallons/ft3 = 816,750 gallons

Best Case = 1/4 acre, cut it all in half.

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Let's say 400,000 gallons best case, 800,000 gallons worst case. At 45 degrees.

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Now, you pump 100 gpm 24/7. That's 6000 gpHour, which makes 144,000 gallons per day. At 67 degrees.

For the simplest possible "Mix the water and warm the pond" model, adding 144k gallons at 67 degrees to 400k gallons at 45 degrees would give 544k gallons at

[(144k X 67) + (400k X 45)]/544k = 50.8 degrees, IF the water was added and mixed instantaneously (you would need a really good spillway or drain in this case )

Worst case, the simplified model raised temp would be

[(144k X 67) + (800k X 45)]/944k = 48.4 degrees

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Now, how bad an estimate of raising temperature is the simplified, mix-it-all-at-once model above?

I believe that the temps predicted above are an upper limit that will not be met in reality. This is due to the fact that since the warm water is added over a 24 hour period, instead of instantaneously, the cold Winter (air) temperatures will be lowering the temperature of the well water after it enters the pond and before all 144,00 gallons of it can warm the pond up to the above temps (50.8 or 48.4 degrees). My brain is not working well enough to explain this prediction better right now, but the effect has matched experimental results I have obtained pumping cool water into warm water while heating the overall mixture, albeit in the opposite direction (cooling versus warming).

I would be very interested in Cecil or another high-volume well/small pond 24/7 pumper making a prediction of what your upper well-warmed pond temp might be, and would place a greater emphasis on a good estimate based on real-life, real-pond experience than on my theoretical projection shown above.

I'm depressed.. But thanks for the math..

You just need a smaller venue to overwinter the tilapia in. If you had a micropond like Meadowlark's, 100 gpm at 67 degrees would keep the temp up easy; your biggest problem might be non-cooling aeration of all the well water.

I was unsuccessful trying to find ML's micropond thread - hey ML, what's the link?

Also check out Ryan Freeze's Tilapia overwintering in a tank, IIRC on the order of 1500 gallons. Here, I believe.

I couldn't help adding some engineering calculations to this discussion.
To calculate heat gain / loss, you would need to take into consideration the
1. Heat loss due to evaporation. This will be impacted by the surface wave action as this impacts the film layer evaporation due to surface layer humidity.
2. Heat loss due to convection.
3. Heat gain due to short wave radiation (UV solar gain)
4. Heat loss due to long wave radiation (IR losses to the atmosphere)
5. Heat gain due to fresh water additions.
6. Conduction losses to the surrounding ground.
Using the 1st law of thermodynamics,
dH/dt= sigma(Qin-Qout)
you could calclate the heat losses, but this would still only be a guess.

I have all of them except for # 5.

Maybe this test is going to fail.. But I'm going give it a big time try..

me too dave, it'd be funny if it werent so sad.

i dont know anything about tilapia or much about mixing thermodynamics but had a couple thoughts.....

first, do tilapia hang in the shallows, the deep, or all over pond?

if adding water of different chemistry and temperature with no circulation or aeration i could imagine you could create a thermocline or stratified body of water. if you add the water to the top you get an upper warm layer through winter. if you add the water from bottom a) you get warmer conditions at bottom and b) you induce more mixing (not necessarily desirable in larger pond) as the warm water wants to rise through the cold.

so if tilapia have a preferred place to hang out, add the well water at the appropriate depth.

ok, blow my theory out of the pond

A couple of thoughts, I have caught them deep and shallow, so I am guessing they roam the pond top to bottom. If you had an area that was warmer, like the place where your water was being introduced, I believe that is where they would go, if in doubt feed them in the warm area and they will definitely go there. Solar swimming pool covers might increase the water tempertures in small areas.

I'm thinking he needs to try to build a warmer place for them. Make sure the water is aereated and where it comes into the pond, use some plywood or some other junk to create a shelter like you would a dog or cattle. Maybe run the water into a 55 gallon drum with a hole in it for them to enter.

There's an idea - a little corner of the pond, screened off (tilapia in, other fish out), mostly walled off (to allow a little, but only a little, of the water to exchange with the rest of the pond), insulated on top (pool blanket?), fed, and heated (small area might be possible). It might work. Would it be less trouble than a separate tank???