I need to fill my indoor pond it's 100gal and I have a garden hose connected to are city water supply right outside my window, and was wondering if it would be safe to feed it through my window and use it to fill the tank up ???
1) If are setting up the tank and need an easy way to fill the tank with water then yes, a garden hose is fine.
2) If already have the tank setup and are looking to use the hose for water changes and to top off your tank then no, the hose is not a good idea for a tropical tank. The water would probably be too cold to add to your tank. You want to add water that is about the same temperature as your tank.
If #2 is what you're trying to accomplish then I HIGHLY suggest you look at getting the Python. It's the best way I've found to clean and fill my tank. It attaches to MOST sink faucets.