Because the fish need the enough amount of water every day of their lives
evapouration
It will cool down water temperature when by melting down AND it will lift up the water level in the aquarium
Evaporation.
The fish are drinking it. Get rid of the fish
You need to get a water pump and filter for the aquarium at a pet store.
Do water changes, and use aquarium salt at around 1tsp per gallon
There should be a line indicating how far they go down in the water
You can do a water change while it is cycling, but that might slow down the process.
As far as the running of the tank and the efficiency of the filter is concerned, it doesn't matter if the water splashes down into the tank or flows quietly into it provided you are getting a maximum flow and the filter is cycled.
the water level would sink. Anything that sinks into the water would cause the water level to sink
A canyon is formed by a river. The river rises to the highest point and starts to carve. Then from there the water level goes down... And there's your canyon:-p
When a river floods, its crest is the highest level the floodwaters reach. After the crest, the river level starts going down.