13 yr. old irridecnt black shark

Question
I just inherited a 75 gallon tank and a thirteen year old fish.  The previous owner told me that he does a 50% water change and only adds melafix to the tank from tap water.  Is that enough to condition the water?  I already replace the water but am scared that the melafix is not enough to take care of the chlorine in the water i live in a town that uses well water.

Answer
Well water is known to cause algae in the tank. Melafix is a medicine not a water conditioner buy some proper water conditioner.

The Iridescent Shark is more then likely stunted. They get 4 feet in length and need a 1000-2000 gallon aquarium with triple filtration.