I shifted my heat mat and thermostat from a plastic tub to a glass tank and while before it was going on and off all the time (showing that it was working correctly) now it's going on and off very far in between.

In the first setup the thermostat probe was positioned underneath the tub, between the table and the heatmat, while now it is taped underneath the heatmat but not touching the table (since it doesn't fit underneath the tank), is that the reason?

The tank is already lifted some 1/8 " from the table, do you suggest I use more spacers to lift the tank a little more (around 1/3" - 1/2" ) so that I could stick the t-stat probe in between the heatmat and the table or between tank and heatmat again?

Thanks