I just bought three GloFish at PetSmart and put them in a tank I had ready at home. One of them stays at the top, sometimes it's two of them. The others stay near the wall.

Petsmart said that my chlorine, nitrate and nitrite levels were fine. I have been running my tank before getting the fish for about a week. I have no algae in the tank, and everything I have is by TopFin. I have a 10 gallon tank. My filter is running fine (I think, the indicator is blue, not red), and my heater runs at 78 degrees Fahrenheit (around 26 degrees Celsius). I have not fed them, as they were fed at the store.

I am scared, as another user said all 7 of his GloFish died.

What do I do? Should I replace the water? Should I increase the tank water volume beyond 10 gallons?

Edit: Sadly, they died.

  • Did you let the goldfish acclimate to the water temp before you released them from the (store) bag?
    – elbrant
    Commented Feb 24, 2019 at 4:00
  • 1
    @elbrant it is about glofish not goldfish en.wikipedia.org/wiki/GloFish Commented Feb 25, 2019 at 10:55
  • 1
    please do not let one setback stop you from having a living little ecosystem in your house,read and learn about how to do it right and you will have the fish for many years to come.most of us that have fish have been where you are now :) Commented Feb 25, 2019 at 11:12
  • @trondhansen omg, a typo, heaven forbid... you would still acclimate new fish before releasing them into the tank, right?
    – elbrant
    Commented Feb 25, 2019 at 19:17
  • 2
    one need to take it slow when adding new fish to any tank or for me to my pond :) in fact it is best to get fish from a local shop that have the same water supply as you have to lower the amount of stress for the fish. Commented Feb 25, 2019 at 20:25

2 Answers 2


Sorry to hear about your fish. Please don't despair, a lot of shops set you up to fail. From the sounds of what you've written in your question, you did everything right.

Firstly, make sure you read about the nitrogen cycle. If you read and understand one thing about fish, this is probably the most helpful.

Secondly, get yourself a test kit. You can either get a liquid one or the strips but beware, whilst the liquid one is much more expensive, it lasts a lot longer and gives better readings. The liquid one gives you the most important reading for a new tank, which is ammonia.

What happened?

From reading your question it sounds like ammonia poisoning--it's a little tricky to say exactly over the internet, but this is normally the most common stumbling block in new aquariums. Running the tank for a week won't necessarily ensure it is cycled because if there is no source of ammonia, there will be no bacteria to convert it and it may just run clean for a week. Check out this guide on cycling a new tank: https://www.youtube.com/watch?v=eBMgppmFyoE

Much of fish keeping is dealing with water chemistry. Any ammonia in the water at all will be lethal to fish.

What next?

Please don't give up with fish. They can be an incredibly rewarding pet to keep. This time, make sure you've tested the water yourself (a lot of shops don't even test for ammonia when they test it for you). Make sure you follow one of the methods in the video I posted above.

Do all your homework first before getting the fish; it can be tempting to do it sooner but it's definitely better to wait until the levels are showing correctly.


Replacing the water is not the way to keep your fish alive.

What you need to do is change about 10% of the water once a week and be sure not to overfeed the fish.

You might feed a little once every 3 days until your tank is in biological balance.

You need to buy a water test and test the water every other day for the first week. You will probably get an ammonia or nitrite spike within a week or two, and if you do, cut the feeding and replace 20% of the water every two days until the nitrite or ammonia spike is over.

Here is some reading you have to do to understand how and why the cycling of your tank is needed.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.