guppies and cloudy tank

Question
Hello my wife and i lost 21 guppies in one day.
We keep up with the maintenance.The fish started dying when the tank got cloudy.
We took the water out and thoroughly cleaned the tank filter and the artificial plants.And i went to the store and bought 4-2.5   gallons of water.it was the drinking water.when we refilled the tank the water was crystal clear.we bought more fish and we get the fish from a fish store.when we put the fish in tank that we purchased,the tank is cloudy again.We put the bags that they put fish in,in the water in tank.after a while we emptied the fish in tank and the cloudyness is back.
Any idea on what might be the problem?
Thanks,Edward

Answer
Hi Edward:  Your tank is cycling... the fish died because the water chemistry spiked... this often occurs when tanks are cycling and a key indicator of cycling is cloudy water.  The tank needs to find a balance between waste in the tank and beneficial bacteria. When you clean the tank too well or take out too much water it depletes the beneficial bacteria and the water chemistry spikes to unsafe levels.  I would add some beneficial bacteria to the tank. You can get that at the local pet store.  Look for products called CYCLE or Nitromax both work the same.  dave