The oxygenator is a real good and inexspensive option to the battery units. They make 100% pure oxygen. I have one of the portable units, I got at Gander Mtn at Bowling Green for around 75 $.It hooks directally to your main battery, I ran a switch to mine,but it only comes on when it is in the water. Go to keepfishalive.com to see in action. I was leary at first but these things work. the fish seem to hover over mine. I fill the liveweel up first thing in the morning and then only have to add fresh water every hour or so, as to get rid of any waste and also add their U2 formula, have not lost a fish since using this system,and I had a very bad problem before as my liveweel only has pump in not recirculate. As for water temp as lone as they have Oxygen in the water the temp does not matter, unless it is 100 or more. The reason to add ice is that Oxygen disolves slower in cooler water than warm, so you dont need to add ice with this unit. All my fish have been very active and livley even after all day in the livewell. It is a good unit and worth it and you have no old batterys to throw away. I also tried on of the other kind liked mentioned above and it did not do as good a job as the Oxygenator .