Kenan, welcome to TFF.
Bioactive will not soften hard water. It is a bacterial additive presumably intended to initiate/strengthen the nitrifying bacteria (what we term the cycle or cycling). It has no effect upon water hardness/softness or anything else.
As JuiceBox52 posted, you/we first need to know the GH of your source (tap) water. And the pH while we're at it, and if you know, the KH (carbonate hardness or Alkalinity) is useful. You may be able to ascertain these from your water authority, check their website or contact them.
Water hardness (GH) is primarily the level of dissolved calcium and magnesium minerals in the water. The KH is related to this, as is the pH though some other factors also affect these. But basically you need to reduce/remove the dissolved mineral in order to soften the water.
Hard water can only be safely and effectively softened by diluting it with some form of pure water. Rainwater can be used (if otherwise safe), or Reverse Osmosis water. You can buy RO water, or you can have a RO unit installed on one of your taps. RO water is pure water, with zero GH and KH and a neutral pH (7.0). Mixing RO and tap water will reduce the GH proportionally, for example, half RO and half tap will result in a GH that is half what it is now. When we have the GH and pH, and the KH if you can find it, we can consider options.
The problem with the fish may have to do with the GH, or the pH, or both; I am also wondering if cycling is also involved. Now we have questions.
How long has this tank been set up? How long have you had the fish? Are there live plants? How did you cycle the tank? Are you doing water changes, and if so, how much and how often?
