a fish dies every day help

im taking out all the river rocks today and iv got some stuff coming this afternoon that's ment to make rain water safe for fish , ill let you no its name ect when I get it , had 3 more looking sick yesterday all sitting on the bottom so iv taken then 3 out put into hospital tank they are still sitting on bottom but today they are still alive so hope they make it , and no there was nothing left in tank after salt water was used , when I got it ,it had leak so I had to fix that so tank was filled and refilled a few times so it had good wash out ,
What stuff to make the rain water safe? If it's contaminants from the roof or something, it's probably not something your typical water treatments will be able to handle.
 
Solve your dying fish problem before worrying about adding river rocks to the tank.

Two things scream out at me here after reading this thread.

1. You're collecting rainwater from your rooftop. This means that the water is picking up anything on your rooftop (particles, chemicals, dirt), and it's being deposited in your tank. There's countless things that could be coming off your roof that could be harmful to your fish. How high is the pH on your tap? A stable pH is far more important than "the right" pH. You may be able to get away with using tap water for your fish.

2. You mentioned a problem with your heater. This is an easy way to kill off a lot of fish, very fast. In fact, I had a similar issue with a new fish dying every day in one of my tanks, until I realized the heater had broken. 23c, while at the low end of the tolerance for your fish, I wouldn't expect to see harm them. However, if it's been broken for a while, and the temp has been dipping much lower than that during the night, it could very easily be the cause.
 
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