[playfoot99]

I recently did my first water change as a beginner which ended in disaster... I have a 37 gallon tank with 6 molly fish and I did my first water change (10% water change) in this tank by replacing the water with treated tap water but I found 3 of my mollies were dead and when I tested the water nitrite was still very high - even the next morning.

I didn't want to overtreat the water and as a beginner I presumed that I only needed to treat what was being added back but I guess I incorrectly dosed? If anyone else has more experience and any ideas on my molly fish deaths let me know, it would be greatly appreciated.

 

[susankat]

How long has the tank been set up and what are you using to treat water. Can you give me all your parameters ph ammonia, nitrites and nitrates. Actual numbers. It sounds like the tank isn't cycled and you need to do large water changes to save your fish. Like 50% daily until it is.

 

[playfoot99]

The tank is 20 days old so I agree with you that it isn't cycled.. I will continue to do water changes to reduce nitrite buildup until cycled. Thanks!

 

[susankat]

It's going to take awhile, keep an eye on ammonia and nitrites. Fi s Hemlock in cycle can take 6 to 8 weeks to finish, a cycle without fish can take 4 to 6 weeks.