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Heat generated by Pacus


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Last colony, I had a lot of Pacus in a large pool, probably around 40. I found that I needed to do active cooling to keep it below 25C to keep them reliable alive. My guess is the heating comes from Tropical Pacus being born warmer that 25C and maybe regular ones being as well. 

Does anybody have any actual numbers on how strong this effect is? If not, I am probably going to do my own measurements next colony, but I thought I would ask first.

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So, what's happening here is that everything has a spawn in temperature and for critters, they get reset to that twice - once when they hatch, and once when they become adults. In the case of Pacu (and variants) those temperatures are:
Gulp fish: -12.5C
Pacu: 30C
Tropical Pacu: 50C

It's not so much that your fish are producing heat, it's just that they "arrive" with some.

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57 minutes ago, Autoskip said:

So, what's happening here is that everything has a spawn in temperature and for critters, they get reset to that twice - once when they hatch, and once when they become adults. In the case of Pacu (and variants) those temperatures are:
Gulp fish: -12.5C
Pacu: 30C
Tropical Pacu: 50C

Thanks for the numbers. So regular Pacu are already a problem for Gulp Fish. That should allow some estimates.

Soo:  Mass: Egg: 4kg   Fry/Adult: 200kg  

I think we can ignore the eggs here for a minor error. With material being Genetic Ooze at 3.470 DTU/(g * C), the temperatures you state and 22C target temperature (to have some safety margin) that means:

  • One Gulp fish adds 2 * 200'000g * -34.5C * 3.470 = - 47.9 MDTU 
    =>  Cooling needed -1.92 MDTU/cycle = -3.2 kDTU/s
  • One Pacu adds 2 * 200'000 * 8 * 3.470 = 11.1 MDTU 
    =>  Cooling needed  444kDTU/cycle = 740DTU/s 
  • One Tropical Pacu adds 2 * 200'000 * 28 * 3.470 = 38.9 MDTU 
    =>  Cooling needed 1.56MDTU/cycle = 2.6kDTU/s  

The problem are the regular Pacus, with Gulp Fish and Tropical Pacu basically cancelling each other out as they have pretty much the same probabilities at 22C (slight advantage to Gulp Fish in the temperature, so treating them as equal adds safety margin) .

Hence to keep 1 Pacu at 22C, you need to provide 740DTU/s of cooling.

That is quite a bit with a larger number of fish and nicely explains my observations. 

 

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Would be nice to do the same calculation for dreckos and glossy dreckos, i usually keep those until they grow up, shear them and then murder them because otherwise they heat up the area too much. They also come out of the egg at a rather high temperature.

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51 minutes ago, NeoDeusMachina said:

Would be nice to do the same calculation for dreckos and glossy dreckos, i usually keep those until they grow up, shear them and then murder them because otherwise they heat up the area too much. They also come out of the egg at a rather high temperature.

You can just plug-in the numbers if you have them. It is basically

2 * (weight in g) * (temperature difference in C) * (SHC of material, probably 3.470 DTU/(g * C)) = Total amount of energy for 1 critter to be absorbed

Divide by critter lifetime in cycles and by 600 and you have the cooling power you need to provide for that.

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53 minutes ago, NeoDeusMachina said:

Would be nice to do the same calculation for dreckos and glossy dreckos, i usually keep those until they grow up, shear them and then murder them because otherwise they heat up the area too much. They also come out of the egg at a rather high temperature.

Always keep your dreckos in an insulated ranch, as I learned the hard way.

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1 hour ago, NeoDeusMachina said:

Would be nice to do the same calculation for dreckos and glossy dreckos,

Dreckos: 62.5C

Glossy Dreckos: 42.5C

eggs spawn at 20C

critters are 200kg, eggs are 2kg

The calculations depend on what target temperature you want obviously.

 

1 hour ago, NeoDeusMachina said:

i usually keep those until they grow up, shear them and then murder them because otherwise they heat up the area too much.

Just insulate them.  My egg overflow/ starvation sheering rooms looks like this.

2045884706_Screenshotfrom2021-07-0913-24-18.thumb.png.49b359199a954714ad34b712937b5624.png

It gets toasty, but not enough to hurt anything.  And the small amount of heat that leaks through the liquid lock is taken care of by regular base cooling.  You could use a vacuum insulated double liquid lock and prevent all heat leakage, but that would interfere with my egg delivery system.

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15 minutes ago, ghkbrew said:

Just insulate them.  My egg overflow/ starvation sheering rooms looks like this.

It gets toasty, but not enough to hurt anything. 

And that is the problem with Pacus: It gets hot enough that Gulp Fish die, and hence a non-cooled Pacu pool depopulates over time. For critters that do not have that problem, just insulate things, I agree. Same if you farm them, because then you have ample resupply.

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1 minute ago, Gurgel said:

And that is the problem with Pacus: It gets hot enough that Gulp Fish die, and hence a non-cooled Pacu pool depopulates over time.

Yeah, though an alternate solution is to segregate the fish populations then insulate them.  Tropical and regular pacu can live in one (hot) pool and gulp fish in another.  It complicates the build a bit but should be competitive size-wise when you add cooling to a 1 pool setup.

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41 minutes ago, ghkbrew said:

Yeah, though an alternate solution is to segregate the fish populations then insulate them.  Tropical and regular pacu can live in one (hot) pool and gulp fish in another.  It complicates the build a bit but should be competitive size-wise when you add cooling to a 1 pool setup.

Doing this should be relatively easy by using auto-sweepers and filters on conveyor loaders for the eggs. Maybe I will try that next time.

34 minutes ago, degr said:

so, if you can keep water 10 - 25C, all species will survive

Yes. But if you do nothing, it will slowly go to 30C.

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I just let my pool heat up until gulp fish eggs don't spawn anymore. 

Also most pacu tanks designs have a breeding section (or can add one for very little space) that can easily replenish any lost pacu.

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1 hour ago, oosyrag said:

I just let my pool heat up until gulp fish eggs don't spawn anymore. 

Also most pacu tanks designs have a breeding section (or can add one for very little space) that can easily replenish any lost pacu.

They should still spawn, just with small probability. Also, the whole discussion is about wild pacu. If you breed them, the loss does not matter.

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