posting this only since I see you have same dolphin model I do...
I went to the Garnet See Level system. The monitor fits nicely right at the top of your control panel area, the wires that were already run for the goofy light level system work fine for the See Level system (capacitive system, no more bum readings).
Apply the new sensor strips to outside of the tank, transfer the wires from the goofy lights to the new control panel, and whoo hoo.
One of the best mods I have done and definitely the easiest (once you are comfy removing the pretty covers in the compartments).
I went with 709 series.