Fish Temperatures

[Pawnic]

Hi Everyone,

 

I live in Austin, TX, and my tank ranges from 74degrees in the morning to 91degrees in mid-afternoon. I don't see fish adapting well to this range at all. It is a glass tank that sits above ground, and it is in shade all day. I plan on putting some shade netting around the tank anyways, to hopefully cool it down a bit more, but I don't think it will make much difference. Does anyone have any suggestions?

[Adam Blanton]

I'm in Austin as well. I've got a 110 gallon tub buried with my grow bed above it to provide shade. The water temps don't get above the low 80's even in this record summer heat wave we're having.

 

How big is your tank and where are you keeping it?

 

Is there any way for you to move the tank indoors or in a garage? Maybe even cover the tank with insulation to help keep the hot air off the walls.

[TCLynx]

What kind of grow beds?  Are they in full sun?  How big is the tank?

 

That is kinda an extreme temp change and more water is my primary recommendation.  I think my 300 gallon fish tanks have gotten over 90 F this summer but the low temperatures overnight are around 80.  Much of the summer lately our air temps have been lows of about 78 and highs in the shade of 104.

 

If you are doing flood and drain media beds, you can probably stabilize temperatures a bit by running constant flood instead but if the system is really small, that might not be enough.  For Year round outdoor systems in the Deep South, I would say having 300 gallons of water circulating round the system some how is probably close to minimum size to allow for flood and drain and keep native fish happy without some active means of temperature control.

[Pawnic]

Hey guys sorry, but it ranges from 79 to 91. This is still a big range though. The tank is 75g sitting directly underneath my grow bed as well. It is in full shade. I am not on a continuous cycle, just a flood and drain 15min on and 45 off. I didn't think about it before, but I think I realize why they are so drastic. One of my half barrels 27.5g is not completely filled with hydroton yet. So the water is being heated in full sun during each flood. After I get the rest of the hydroton in (tomorrow hopefully) I will check again see how the temp ranges. I think this will have a drastic effect.

[Adam Blanton]

The UV rays from the sun will also kill the bacteria in the water, so I'd get those filled up before you put some fish in there!

[David Kipperman]

You might have to get a chiller for the warmer months to keep the tempature more consistent. It will circulate cooler water in the tank and keep the temp the same day or night.

[Calvin Schmidt]

also note that the hydroton will soak up some heat while in full sun, then when it floods it will pass some of that heat to the water.

 

More water and maybe some white shade cloth around the base of the plants to shade the grow media? just a thought

[Wayne Sumrall]

How about a pretty high flow pump to recirculate and aireate (sp) the water. It seems to help for me. My water never gets over 85.

[Johann]

Put your tank in-ground. This would keep your temps very stable.

Make your system bigger, this may narrow your highs and lows, since it would take longer to heat or to cool the bigger value.

If you have grow beds or sump attached to it, paint the outside black first ( barrel system ) and then paint them white ( any of the grow beds or sump). Black will prevent the penetration of lights to protect the roots of getting light and the white color will keep the grow beds or sump cooler since it is reflecting light.

If  you can not or not willing to move the fish tank there is one more solution.

Dry stack solid bricks all around the fish tank. If the brick is 7 inches long that would be the thickness of your wall around the fish tank that would go all the way to the top and maybe 1 or 2 rows above . But leave a 1/2 inch to 1 inch space between brick wall and fish tank to allow for expansion of the glass fish tank. 

What you are after is mass.This is how it works.

Daytime the bricks will heat up and store the heat and at night it will give up heat, this way the water would stay more stable in temperatures. But the heating and cooling would be done slower because of the mass of the  bricks. You may find that the temps may not go up as high as they used to be day time nor will they drop as much at night.

Did you ever touch a brick wall at day time and then touch it again hours later after the sun has set down?.....same principle..

 

 

[TCLynx]

I'll make a note about digging tanks into the ground and flood and drain media systems.

 

Yes, sinking a tank into the ground (in any location where the ground temps stay within the desirable range for your chosen fish) will help some.  If you are in a place where the ground freezes and you want to raise tilapia, insulation will be needed either way.  Anyway, the ground can help some.

 

But it is not as huge a help as we might wish if you are running a flood and drain media bed system.  Here is why.

Flood and drain gravel is a great heat exchanger between the air temp and the water temp.  As the bed drains, the air is drawn down into the bed and will impart some of it's temperature to the media.  When the bed floods again, that temperature imparted to the media will in turn be imparted to the water.  So in the heat of summer afternoons the flood and drain gravel will warm the water and on cold winter nights the flood and drain gravel will chill the water while warming the air.

 

SO, burying the fish tank and putting an insulating cover over it may help some but the flood and drain gravel is gonna be working against you.  I sometimes recommend switching to constant flood and adding more water to the system through the extreme part of the season instead of turning it off.

[Johann]

You are making a valid point.

I think the original poster is concerned about stabilizing the temperature of the tank in his / her area and he / she did not mention to have grow bed's.

TCLynx said:

I'll make a note about digging tanks into the ground and flood and drain media systems.

 

Yes, sinking a tank into the ground (in any location where the ground temps stay within the desirable range for your chosen fish) will help some.  If you are in a place where the ground freezes and you want to raise tilapia, insulation will be needed either way.  Anyway, the ground can help some.

 

But it is not as huge a help as we might wish if you are running a flood and drain media bed system.  Here is why.

Flood and drain gravel is a great heat exchanger between the air temp and the water temp.  As the bed drains, the air is drawn down into the bed and will impart some of it's temperature to the media.  When the bed floods again, that temperature imparted to the media will in turn be imparted to the water.  So in the heat of summer afternoons the flood and drain gravel will warm the water and on cold winter nights the flood and drain gravel will chill the water while warming the air.

 

SO, burying the fish tank and putting an insulating cover over it may help some but the flood and drain gravel is gonna be working against you.  I sometimes recommend switching to constant flood and adding more water to the system through the extreme part of the season instead of turning it off.

[TCLynx]

without some form of grow beds (be they gravel or raft or nft or something else) it isn't really Aquaponics.  Sorry unless some one states otherwise, I'm gonna assume aquaponics since this is an Aquaponics site.

[txdurk]

I'm in Houston. I'm setting up an above ground FT and am worried about the coming summer temps as well. I am thinking I may try 'siding' the exterior of the GB and FT with reflectix. The bubble wrap in the foil may act as an insulating blanket in winter as well. I don't have anything to lose if the temps become unmanageable.