Tank Leaking Above Waterline : O

Have you looked at all the lines? Do you have a bubble wall? One of the things I noticed with mine was that the bubble wall created a lot of extra "mist" at the top of the tank. It traveled up and over the little ledge of the rim material and found it's way down the plastic background picture.

In another set up a way long time ago, the extra activity of a vigorous filter caused the water to creep up the pump housing and down the power cord. That's why they say to loop it I guess so it doesn't drip into the power strip.

I have a similar problem but I have it sussed. This may not apply in your case but... My problem is caused by the water level falling slightly and causing the output from the filter to cause more splashing. This seems to find its way out of the tank by squeezing under the hood. Keeping the water level high cures it.

My first tank used to 'leak' which I traced to condensation from inside the lid dripping down the outside of the tank. I solved it by putting a strip of P shaped draught excluder round the edge with the thin part tight up to the rim and the wide part slotting down on the inside of the glass. If you continue to have problems, this is something else to try.