Ravnis

Overwintering tilapia with minimal heating

10 posts in this topic

It's been a four year project, but preliminary results are encouraging.  I have steadily  been letting the water temperature get lower each winter and spent a lot of money on utilities to keep the tilapia warm enough to get through the winter.   The last few months have been colder than normal and with minimal sunshine the last 3 weeks the water temperature has been hard to keep up.  Water temperatures have been 46F to 52F for the last month with 46-48F this last two weeks. Solar water heating and a forced air heater set at 50F have been the only source of heat other than a single 300 watt heater in a 4000 gallon tank.

 

The water temperature has climbed since last wendsday and the fish are biting my fingers as I check the water temperature now that it's 56F.  It peaked at 60F and I threw a little food to them and they ate it within seconds. I don't want to overload the biofilter that is sure to be weakened by the cold as well.  I will feed minimally and monitor for ammonia buildup.   I did loose 4 fish during this, but do not see any signs of having lost more.  I know the cold weather has wreaked havoc on fellow ap'ers, but wanted to let you know there is hope to reducing utility bills and overwintering fish.  I doubt howerver that they would have had time to acclimate in a smaller volume system. Temperature changes occur over days due to the system volume close to 5000 gallons. 

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Ravnis,

It has indeed been brutal this winter for a lot of us in this country. Glad to see your're adapting. I'm still considering a trombe wall on the south end of a pole building for the building that will house my cool and cold water tanks.

I would love to do some aquaponics with this in the winter with an add on greenhouse but don't like their heat loss at night or on cloudy days.

Edited by Cecil (see edit history)
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Glad to see your results.  When I was doing my water exchange the other day, I realized that water temps were not my only problem.  Like you observed, the cold had overloaded my biofilter.  I had cut off the grow beds to minimize heat loss, and I knew that cold weather affected bacteria, but somehow I didn't make the complete connection.  As things turned out, a handful of my tilapia survived by hiding very close to the heaters.  They are feeble and still might not make it, but I'm giving them all the attention I can.  Fortunately the days have been warmer and the greenhouse has been especially warm, so the water temps have gone up nicely in the day which helps the heaters at night.  I can honestly say I've learned a great deal through this gosh awful winter.  I'm ready for spring and hoping for a 'normal' Georgia winter next time.

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I second your sentiments and experiences Sam. The harsh winter has been quite a learning experience, mostly in very high utility bills. My water temp's were at 59F yesterday, and the fish seem fine - eating normally. Although not as a big a system as Ravnis', the room is insulated well and temp's have come down slowly.

 

I'm so ready for the spring, and hope that next winter is less extreme.

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Making temp's move slowly is a key as well as stopping feeding when anticipating a cold front so the load on the biofilter drops.   

 

Sam, Don't give up hope.  The first year I tried overwintering tilapia  I started having fish mortalities at 57F   and after several generations later they are handling much colder temps.  I think the ones that survived to breed had more cold tolerance.    I think we're all hoping that the major freezes are over for this year.  

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The topic of solar water heater has arisen again.  This site is a treasure trove of ideas.

 

<a data-ipb="nomediaparse" data-cke-saved-href="http://www.builditsolar.com/Experimental/PEXCollector/Construction.htm" href="http://www.builditsolar.com/Experimental/PEXCollector/Construction.htm'>http://www.builditsolar.com/Experimental/PEXCollector/Construction.htm" "="">http://www.builditsolar.com/Experimental/PEXCollector/Construction.htm'>http://www.builditsolar.com/Experimental/PEXCollector/Construction.htm'

 

The solar heater I used in this thread was a 16 foot long version. I got around 4C or 8F degree rise with it.   I used 1/2" pex, but it constricted flow , so if I was to do it again I would consider 3/4" instead.

Edited by Ravnis (see edit history)
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I am not 100% sure of what tilapia we have.  I think it is a blue.  We pulled it out of a really cold stream when it was not even an inch. Cold like refrigerator water.  It is now in room temp and doing just as well.  If our fish is a native and a blue then I question rather they  ( the blues ) need any heat at all.  If it is an escapee from a fish farm it had a long swim to get where we found it. Maybe they mate better in warm water? This one had to be hatched in the late winter.  Even colder water then.  We can buy them full grown at the fish market, alive and ready to eat. That means people do farm them here, somewhere. And also there is a market for them if needed. Regardless I think cold water fish tastes better. I would purge them in very clean cold water, no food for a few days before culling. At the end of the time drop it down so cold that they go to sleep, then enjoy the fish.

 

Maybe if you have cold temp problems, switch to blues. Then the problem should be switching over the bio load back to a filter if the GBs are turned off.  If I had an extra fridge, I would stick him in there and see what different temps do.  I only have fish die here if the water gets too warm. The cold the water the more O2 it can hold.

Edited by Deuem (see edit history)
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Had posted this today in greenhouses but saw your post and thought it might help.....if cross posting is not allowed just delete.

 

his may not work for you but........

I have two greenhouses, a 24'x50' A frame about 15' tall at the peak and a 20'x30 arched.  The larger GH  holds 28 IBC totes with tilapia, 14 totes down each side plus two more IBC totes that each contain home made RDF filters (that are AWESOME)  down the middle of the GH are 6 600 gallon lined tanks.   I use the water in the tanks to not only raise tilapia but also to heat the GH.  I own a fig nursery and start about 2000 fig plant cuttings a year for spring sales and they like to root with bottom heat and they sit on shelves over 3/4 of the top of each tote.   Last winter I relied on 1000' of 1/2" black tubing strung back and forth along the rafters of the GH in 4 runs and pumped water through those lines and back to the main sump.  This system worked but given the volume of water I could only gain 4-5 degrees per day if it was nice and sunny and on a very cold night (28 F) I would lose 6 degrees.   Being in central FL it worked out as we dont get a LOT of cold generally.  Front comes and the tanks drop 10-15 degrees over the course of a few nights then weather gets warm and using thge solar could bring it back up.  Even still if a front came through and stayed cold and especially cold and cloudy it saw a constant loss of temp over several days and lowest the water got to was 50 but last year was a pretty mild winter.  I knew that if we had an exceptionally cold winter that we get perhaps once a decade it could be a real problem and would have a LOT of dead fish and a too cold GH, was just a matter of time.    

Did a lot of reading and finally I settled on a plan.  

My first thought was a wood fired boiler but they use a LOT of wood and are smokey and while I am not in the city i'm also not rural either so I crossed that one off.   What I did was buy a wood fired hot tub heater, think some call them cowboy heaters?  The one I purchased from a company in Canada is called a Timberline volcano.    It is small, 38"H x 27"L x 11.5" wide made from SS and the body is aluminum.  Even that small the manufacturer stated it was 100,000 BTU but I was dubious about that claim to say the least.  The entire heater sits underwater except for the feed shoot that sits 6" or so above the water line and the fill lid acts as the draft control.  I did not want it inside the GH so it was situated about 40' away outside the GH and inside an IBC tote.  I placed the tote so it was the same height as the tanks in the GH.  

Added a second small 1/2 hp dedicated pump and ran a 1" line from one of the IBC totes that holds one of my two homemade RDF filters.   Because the hot water return pipe would flow back to the GH by simply gravity that line was 2".   I knew the ground would chill the water stealing some of the heat in the buried hot water return pipe so I ran 4" non perforated drain line and cut a slit the length of it.  The 2" line was placed inside the 4" line and then made batches with the cement mixer and filled the pipe with a combination of 1 part portland cement, 1 part sand and 6 parts perlite to make lightweight insulating cement.  I wedged the 4" pipe open so i could fill it and when the 4" line was 80% full I laid the 1" supply line from the new pump on top of the 4" line and poured more cement over all of it to a depth of about 2" above the 1" line.  

The IBC Tote that is 40' away and holds the heater I was a bit concerned about it losing heat to the atmosphere especially on a windy day and our cold normally comes with a lot of wind.  My solution was to bury 4 4"x4" PT posts 6" out from each of the corners and built an enclosure around the IBC tote using recycled black plastic twinwall GH material.  In the 6" gap between the twinwall andtote I poured more perlite completely filling that airspace up to about an inch from the top of the tote insulating it.  I added another piece of twinwall to the top and the 6' tall 6" wide smokestack comes out through it.  

The 1" line was run into the tote about 1/2 way down the tote and the 2" heated water line is through the tote 1/2 way down also then elbowed and runs up and pulls the hot water from just 1/2" under the surface.  

To say it worked is a collossal understatement. I was BLOWN away.  On a cold day I would light the heater and in 45 minutes the water at the surface was already 120+ degrees........now if you stick your arm down in the water the water just a foot deep was still cold. You can touch the outside of the heater underwater while the fire roars inside and it was just warm to the touch, maybe 85 degrees or so?  My setup which is roughly 12,000 gallons of water the heater would raise the water temp in the system 1.5 to 2 degrees per hour.  The heater being small uses up very little wood and once burning well is 100% smokeless.  I never even bothered to use the 1000' of 1/2" solar lines at all during the winter.  I would let the heater run 6 or so hours and refill it about once an hour but each fill is only 4 pieces of small firewood.  Once the heater is running(and pump on) temp in to the sump would settle at about 85 degrees and the 1/2 HP Goulds pump pushes a LOT of volume.  It was a dang good idea I put it in as this winter was our coldest in over a decade.  Without that heater the fish would have been dead as we had front after front move through in a 30 day span of time.  With the heater my water never dropped below 65 and I ran the heater total maybe 30 days.  

Also and this was simply an accident.....in the late afternoon I would fill the unit with wood and close the lid/damper completely.  I did it so I would have a nice bed of coals in the morning and would not have to relight it, even though lighting the thing is so easy and fast.  One morning before I had added any wood and the pump was off and had been off since the previous afternoon I was in the GH and happened to walk by the sump and noticed the temperature gauge on the outflow water and it was at 80 degrees.  I looked at the temp gauge in one of the tanks and it was 70 degrees.  Thinking the other  digital gauge was broken I pulled it out and put the sensor in the fish tank where it dropped to also 70 degrees so it was working.  Popped it back into the outflow pipe and put my hand down in to the sump water and sure enough 80 degree water was flowing out of the pipe even with the pump not running. Came back in the house and googled and found the answer I had made an inadvertent thermal siphon.....had no clue such a thing even existed.  So even without the pump running cold water still goes to the tote and warm water still flows back to the sump.  

I plan to drain the heater tote of the fish water and add piping to plumb it in to my inground pool to also heat that, just need to see if chlorine will harm the aluminum before I do it.  

I have no affiliation with Timberline at all and I know other companies sell similar heaters.  If I had had the time I would have probably welded one myself but my aluminum fabrication is generally not pretty, to say the least.  Also was worried I might not be able to get it 100% waterproof.

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I have tilapia in my basement tank that I never heat in the winter anymore. It's cool enough down there I have to wear a sweater when I work in the taxidermy shop. Unfortunately my temp gauge is no longer accurate, but the water definitely feels cool to the touch. I'm guesstimating lower 60's F. Fish feed well once a day. 

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