This new hobby is tough...

[dufreneh]

I set up a 20 gal tank 8 weeks ago. While it was cycling, my wife, bless her, bought me a Butterfly fish and a Clown. At the time, The tank was only two weeks old. Both fish did great for 6 weeks until this past weekend. I noticed they weren't eating and were at the top of the water seemingly gasping for air. I got home from work planning to change some water but the butterfly was already dead. Water params were OK except for Nitrates were about 40. During the water change, my clown died.

I plan on this tank being a QT once my 90 gal is setup in a few weeks. All I have on this 20 gal tank is an Aquaclear 300 filter. No live rock yet. I rinsed the filter media when I did the water change. Could the water have become toxic? I have a hermit that seems to be OK.
Live and learn I guess...

 

[austinsdad]

No live rock yet.

You won't be using live rock in your QT. Copper, when/if needed will kill it.

I rinsed the filter media when I did the water change.

Could've had a problem there. You can wash away the good, nitrate fighting bacteria. Just a maybe. I put a few bio-balls in my hang-on filter for my 20g QT. That way, I can completely change the filter (minus the carbon) when it gets crummy, and still keep the good bacteria.

 

[dufreneh]

Thanks for replying.
I have been using this tank to practice and get a little experience under my belt. In the 90 gal, I will have live sand, live rock, powerheads and skimmer. I did a water change about two weeks ago and everything went well. I didn't rinse the filter though... I just let it run. Although I was too late, I did a water change yesterday anyway. I wanted to save my Clown, but oh well. All that it left is the hermit. I thought the filter might be producing too much Nitrate, so I rinse the media. The media is a foam block, carbon insert and amonia remover insert.