Yes!
Yeah.... uh.... get a freaking filter!
There are two ways to help control water hardness: use a packaged water softener or use a mechanical water softening unit. Packaged water softeners are chemicals that help control water hardness.
Yeah.... uh.... get a freaking filter!
The best way is to control the harness and softness of the source water for the aquarium. If you need soft water, then use a water softener or reverse osmosis machine to lower the water hardness. If you need your water harder, then you can purchase remineralizing compounds that you can mix with water change water and then add to your tank. You can find remineralizers at www.bigalsonline.com. Look under Water Treatment > Ph Regulators & Buffers. I recommend Kent's R/O Right.
There are crystals available in many pet shops that can be placed in a filter to remove hardness. To increase hardness you can add sea shells. To neutralise the water you can get 'Neutralising blocks'. If you are really keen you can use a reverse osmosis filter to remove all the hardness (and other impurities) from the water and then add all the required chemicals to make the water exactly what a specific species requires.
It depends on the softness or hardness, soft water e.g amazon river is acidic so below pH 7 and is caused by things like decaying vegetation and the elements present in the surroundings. Hard water e.g african lakes are alkali so above pH 7, this is again caused by surrounding areas and elements such as calcium which make it alkali. In the aquarium it can be controlled by chemicals which you can buy at pet shops.
My junk
put a filter in
hello
Yes they will die because tropical fish are kept in an aquarium with heat control for the temperature of the water, they will not survive in cold water. Put a tropical fish in cold water it's metabolism will slow down to the point its body no longer works, it won't be able to digest food, will become very lethargic, and die.
You can control the oxygen through aeration
You will have to uninstall it in the control panel.