Does anyone know how liquid air is made?
Air is compressed and a heat exchanger reduces the ambient temperature. The air is then released into a chamber cooling the air even more. (Not going into how the valving is configured)
This process is repeated until the air temperature reaches -320F This is the critical temperature at which all air (N, O, Ar) becomes liquid.
And yes the other gasses as well not mentioned.
Anyone ever let air out of a tire?
In conclusion bringing in cooler air will help but how much is another question.
As for tubing length... shouldn't effect the pumped air temperature much, do to it's plastic poor thermal conduction and the amount of time the air spends traveling through the tubing. Also the air is still not released until it reaches the airstone.
My tubes are warmer at the pump but considerably cooler before they enter the bucket.
A short tubing length is IMPORTANT more for pressure loss over distance since the smaller the surface area of the bubble the more DO imparted into the water.
My advice...Do what you have to control water temp and in the mean time plan and save up for a chiller.
Time is money and so is good crop yield!