There are 2 solutions to your chilling problems that i'm able to come up with first is put all 10 tanks in a bath and chill the surrounding bath water the bath doesn't have to be very deep, or you can put a large container of water at the end of the ten tanks and run a super long tube with coiled sections of tubing in each tank so that your circulating only the large container of water but the heat transfer will happen with the coils of each of the 10 tanks.