Help, fish dying for no apparent reason...?

[lilikitten96]

The ultimate fish newbie here! I set up my tank in January this year with my friend's help (she works in a pet shop and has training with setting up tanks, fish ect.) and its been completely empty since then until last week, I've done regular cleans and its passed all water tests including ammonia so it was ready for when I was able to get fish.

So last Friday my friend set me up with a female and male Gourami and said they were hardy fish so were good for new tanks. I followed all the procedures for putting them in the tank and they seems fine. The female was a bit lethargic, mostly sticking to hiding behind a tree trunk model.

Yesterday evening however the male starting acting weird, he's been a relatively lively fish until then but now he was not swimming around as much and what not. They're both still eating at this point just a mood shift in both of them.

I went to bed a little worried, woke up this morning and the male is dead and the female is 100 times more lively that when she first went in the tank? My boyfriend came to his own conclusion that she killed the male.

I don't really understand? Please help.

 

[LyraGuppi]

How big is your tank? Do you know what kind of gourami they are?

 

[StevenF]

Prior to adding your fish did you ever add ammonia or fish food to the water? You might want to read this.http://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/
A tank with just water and water changes is not chemically active. As a result it will generally not have ammonia, nitrite, and nitrate. However once you add fish there is active chemistry going on in the water. At this time ammonia, nitrite and nitrate will start to appear. Over time this will cause bacteria to start to grow in the tank and then the bacteria will consume the ammonia and nitrite which are toxic to fish.

So most of the time when a beginner sets up an aquarium there is no bacteria in the water to consume the toxins created by fish waste. And the ammonia and nitrite kill the fish. what are your ammonia, nitrite, and nitrate levels right now?