For folks that wanna know the technical stuff, (and to prove i wasnt just talking out of no where regarding temps) here are some experiments i did. I had to dig them out from few years ago when i did them. some are screen shots or pics taken by my phone camera so appologies for sub quality.
This pic shows temp inside one of our most common styrofoam box. This box is subjected to ambient temp of a cold night during travel. This is a normal cooler night with temp averaging about 40F.
From the time it was packed and sent at 7pm, temps dropped to deadly by 1030pm. These fish will not survive.
This nest pic shows same box subjected to freezing temps without heat packs. Avg temp at night would be below 20F. These fish never will have a chance to survive. temps dropped deadly within 2-4 hrs of packing.
This next pic is of same box with 1 heat pack on a normal cool day where ambient temps are about avg 50-60F. These fish will arrive well within range and likely will not have any doa.
Compare the same box with 2 heat packs on a freezing night with avg temp below 40 likely 25-35F. By the time you get the fish they will be almost on the lower end of good range.
This is why we dont use 3 or more heat packs, At about 2-3 hrs they will get so hot that they will fry the fish.
In my early days i tried thermal bags/liners to ship. This chart shpws they are just not as efficient as compared to styrofoam.
This chart shows same box in summer time. No cold pack vs 1 vs 2 cold packs. No cold pack and 1 cold pack will be sufficent to ship in these ambient temps of 80F plus. 2 cols packs will dip the temp too low to cause death in some sensitive fish.
This last chart shows the difference between Liner vs styro vs styro with no cold pack vs 2 cold packs and 3 cold packs.
In this I learned 3 will kill the fish with 2 cold packs almost dipping too low as well.
I have also done experiments with some say use 2 holes with a heat pack so O2 can flow and they can glow better etc, On a normal day it does make a difference of 2-5 degrees inside the box but on cold freezing nights it does not help and in some cases leaked heat out.
I hope this helps people that really wanna understand the science behinf shipping.
This is also for the ones that say Dr Reef does not know how to ship. Well evidence is right here. I did many experiments on how to ship and also trained with 4 major wholesalers in order to be good at it.
I have same equipment /bags / liners and boxes they use and same method they use. only difference in their shipping and mine which makes a huge difference is they ship cargo. I ship UPS.
Cargo works differently. Most of them ship southwest cargo. Wholsesaler packs the box and hand delivers it to southwest cargo, where it sits inside a climate control room till loaded on the commercial plane. Then it arrive directly to your airport within few hours of flight time and into my hands. Commercial planes have livestock special compartments where they are also climeate controlled.
Freight companies do not operate like that. boxes sit outside and planes and trucks are not climate controlled.