am not sure what kind of heaters you were using. The kind I use turn on when the temperature of the water gets near freezing and turns off when the temperature gets up to 40 degrees. There is no welded cage. I use a stock tank deicer.
I used both kinds. A de-icer type - neither of the two I bought worked brand new out of the box and water froze . Then the heater style rated for buckets, hence the cage that keeps the heater from touching the bucket. And that worked....too well...water was steaming hot. Then the cage quickly rusted at the welds.