I am trying to cycle a new...

Question
I am trying to cycle a new tank.  I have followed the directions in "The Simple Guide to Freshwater Aquariums" exactly.  Two weeks ago I put 3 danios in my spotlessly clean 10-gallon tank.  I tested for ammonia and nitrites each day and the level was 0 each time.  Today, with no warning symptoms at all, 2 of them died.  When I have cycled a tank before, the ammonia level went up after just a few days, then it went down & the nitrite level went up, & then finally the nitrate level would go up to a safe level.  And each time an ammonia level or nitrite level were high, I did a 30-50% water change.  I don't understand what happened this time?  Any ideas?  I kept the water temp at 78 degrees and fed sparingly and did all the other things right that you are supposed to do.  I've had a tank for 14 years so I'm not exactly a novice.  I just can't figure out why the ammonia level doesn't go up with 3 fish in the tank & why fish die if the water is "perfect."

Answer
Hi Kathie,
It just goes to show that Murphy's Law is in effect in the aquarium hobby. Even seasoned experts lose fish. My guess is that you did not condition the water with organic biology (a product like Cycle)  and that changing out 30-50%was too much. Even if you think you kept the temperature at 78, if it is even two degrees difference, it can kill fish. It's difficult during the winter to get the water to the perfect temperature.
Anyway, don't take it too hard. Try try again is the right attitude.
I want to offer you my page for easy aquarium care. Read and compare to the instructions in "Simple Guide" and see if  you like my system better.
http://steamboats.com/aquarium.html
Nori