How to keep a wall power supply from dyeing?
simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Simple current limiter with built-in analog current level indication.

Try adding a couple of car tail-lamps. They will reduce the power available at the electrode. If the reduction is too much try a single 21 W brake lamp. Your PSU is only rated for 14.4 W (12 x 1.2) so you wouldn't leave the lamp on deliberately but it's unlikely to suffer permanent damage.