'Put in the water'? Im guessing you mean hydroponics. If not, then just ignore this post.
I think youve put the seedling in the hydro kit too soon... I have no experience with hydro, but Ive read from quite a few people that you should only put the plant in the hydro medium after the 4th or 5th node has formed - with a good light, after about a month.
Oh, and the fan - try not to have the fan blowing wind DIRECTLY on the plant, if its too strong (even on its lowest setting). Try pointing it in the corner of your growroom, or if you have lights which heat up a lot (HID, Sodium, Halogen etc) then have the fan pointing at the light, which will still cool the room down and provide some artificial wind so the plants stem will grow stronger and thicker (like me )