Well... yes... but then you have no way of knowing that the placement of the fishtank was in any way connected to the job opportunity.
Many things happened together that day: you ate breakfast, you left the house heading in a certain direction, the day was auspicious for you as seen through your bazi, you wore something red....why assume it was this particular thing?
Remove the tank and see if the job disappears
Or place a bigger fishtank and see if you get a bigger opportunity!
Then you can know if it really is a "scientific fact"