I purchased a 125 gals. saltwater tank with every thing needed to this tank to run. It started out saltwater was kept up as saltwater until 2 yrs ago. The people I bought it from got tired of the money and up keep on it. They have been pouring tap water into it for 2 yrs. now. Have two fish still living in it. All the coral etc. has died. I bought it to make into a freshwater tank.Any suggestions on what I need to do and what I can use. It has several lbs of rock with it. Has filter, proteim sh, lights that change when needed to adjust to outside light.

That's sad. Corals are very expensive. I wonder why they didn't just sell them off.

What two fish are still living in it? Are they freshwater fish or saltwater?

You might need to get different bulbs for the light. Reef tanks require a different spectrum that can cause algae outbreaks in freshwater tanks.

You can sell the protein skimmer.