Chiller made out of freezer.

To make a chiller out of an up right freezer, this is what I did in the eighties!
Well till I could afford an actual chiller.
I drilled through the top for in and a return, then put in place a large pre filtered power head in the rear of my tank to force water into the freezer.
I made up glass boxes using 7 mill glass each of one-inch top to bottom by just under the inside size of the freezer and a pipe to each one.
There were roughly 40 something of them that took months to make like a block of apartments and all plumbed to each other on opposing corners and those pipes were epoxy resined in and glass strips up the sides to make it all one piece.
Then I got a manual thermostat dial controller and wired it to the freezer then on the thick end of the copper tube that senses temperature, I got a glass test tube and filled with freshwater and sat the end of the thermostat in that water and sealed it in there with silicon, then sat the test tube in the rear of my tanks bio filter and that sensed my waters temp and switched the freezer off and on automatically to the temp I set the dial to.
Worked well but a bit noisy next the dining room table as the water was forced through all those little boxes of glass and back into the tank.
It work fine, that freezer could get my 3 foot high tank down to 18c on a 35c day easily and that house was a hot one. But as I said it was noisy, gurgling!