what I do is I put it in the gravel and start it flowing, I then lift it up out of the gravel and move it across and put it in the gravel again. Repeat till you've removed enough water.
I was going to use the same guy, but because it had to have a transformer added it ended being more expensive than similar things off ebay I didn't buy from him, glad I didn't, sad that you had to have this happen.
ask for a refund and send it back. He's a commercial trader so has to act accordingly under the fairtrade act and consumer guarantees act. Say it's not fit for purpose and return it. Even threaten fair go.
and contact trademe