Tando,
We here at Aquaria Central all share a common love for aquaria, but more importantly, we also share a respect for the life we keep in those little glass boxes. The kind of person that would suggest flushing a fish after you are finished "using it" obviously has very little respect for life. Seek help, and give up on giving fish keeping advice.
To anyone reading this thread that thought his suggestion was ever worth considering, please listen to the good advice on this board regarding cycling. Fishless cycling is both better for your tank in the long run, and far less cruel to the fish doing the cycling. It is the mature, responsible way of doing things. I've been in this hobby for almost 20 years now, and fishless is the way to go.