Why Are My Fish Dead?

HI so I'm new to the aquarium world, did a lot of research before starting though. I have a 20 gal tank with a filter and heater and I had it setup for about a week before I got fish. I got 4 zebra danio on Wednesday, let the water acclimate before putting them in the tank. They swam on their own out of the bag. They seemed to be doing quite well, very active, feeding fine. Then this morning one was dead and by the afternoon so was another. Any thoughts on what could be happening?

And of course I had named them all last night.

RIP Number One and Swirly

 

When you "set it up" did you cycle it? And are you planning on getting more danios?

 

Do you know about the Nitrogen Cycle? Do you have a testing kit?

If you only let the tank sit for a week, and didn't add ammonia, it probably wasn't cycled.

 

Friendly tip for the future: Never add the pet store water to your tank. It has nothing to do with the deaths but it’s knowledge worth having. For now I’m going to say ditto on what the other two replies said and wait on you to give us some insight into your knowledge of the nitrogen cycle and whether or not you have a test kit.

Edit: Oh! And I nearly forgot, zebra danios are schooling fish and to be happy and healthy it’s recommended you get 6 at least. Otherwise they may get a little rowdy and nip fins.

 

Also to acclimate the fish you need to add a little bit of your water to their bag over time. Floating the bag just acclimates them to your temperature.

 

Sorry to say it, but your fish were probably poisoned by their own waste. Google "Fishless Cycle" and follow the instructions. It usually takes a month to 6 weeks.

You want to have a colony of beneficial bacteria growing in your filter and gravel before you add any fish. These bacteria break down fish waste and detoxify your water. As others have said, a water test kit is a great idea. But you can also take your water to most fish stores and they'll test it for you. But the key is to start the nitrogen cycle yourself and be patient. Good luck.

 

Well your not the first to have this happen to. All good info above. Unforunatly your going to be doing a fish in cycle unless the last 2 also have passed. I allways do fish in cycling so it’s not a problem. What you have to do now is do 30-50% water changes daily. Get a test kit. There’s many reasons why your fish could have died. Best to add water to bag when acclimating. Most likely died from stress. How are the rest doing?