How high can I fill a Jebo tank?

[garninine]

I have recently bought and set up a small secondhand Jebo R310 tank for a couple of gold fish. It did not come with an instruction manual. It has a filter unit tube with a small box at the top. The power cord appears to go into the top of this box so I want to know the maximum level I can safely fill it up to. At the moment I have the water level about an 3/4" below the cord but the waterline is 2" below the top of the glass. Can I fill it any higher without risking getting water too close to the electrics?

Thanks

 

[tackful]

I would be reluctant to submerge the power cord inlet without specific instructions from the manufacturer. Is it possible to raise the tube so that you can add more water without submerging the cord?