Pets Keepers Guide Forums

Hi,
I wasn't able to start a new thread, so I'm posting here.  I have a similar question as the original poster.  

We got our daughter a 10 gallon tank, cleaned all the gravel and decorations (without soap of course), and added water conditioner to the water.  The tank has a heater and a filter that moves the water.  We did not do a fishless cycle originally.  We let the tank run for a few days, got 2 glofish tetras, and added them to the tank.  After about 3 hours they started to swim the to surface, with their mouths opening and closing at the surface.  They both died within a 4 hour time period.  We returned them, talked to the people at the store.  They tested our water and everything looked fine.  They thought that perhaps there wasn't enough oxygen.  We got a moss ball, as well as an airstone, pump, and tubing and hooked that up and let it run for awhile.  We got 2 new fish then, and they died after 7 hours.  They had started swimming to the top, as well, after about 5 hours.  We floated their bags when we got them for about 15 minutes, then added some of our water and let them sit for another 15 minutes, then added them to the tank.   

What do you think caused them to die so quickly? 

We have since emptied our tank, we got water and substrate from a friend who has an established, thriving tank.  When I tested it last night, it showed 0 levels of ammonia and nitrites, and the nitrate reading showed about 20.  PH was 6.2, hardness 300, Chlorine was 0, and alkalinity was the lowest reading.  What should we do to maintain this water in order to get it ready for fish?  We just put the water and substrate in yesterday.  

Thanks for any help you can give us.

Hello, Fishtastic.  Welcome to the forum!  


When fish died within hours, it is most likely due to either chlorine or shock.   

Did you use the aquarium water conditioner according to the instruction on the bottle?  What water conditioner are you using?   While it is unlikely you have overdosed, but I just want to make sure this is not the problem.   

Did you acclimate your fish when you add them to the new fish tank?   Fish acclimation is critical when you introduce new fish to a new tank.   

The water fish came with has different water temperature, PH, hardness, among other things.   If the difference between the water in the plastic bag the fish came in with is too big compared to the water in the fish tank, the fish will get into shock and may die in hours.   

For details on fish acclimation, you may read the following article -
3 Important Steps to Introduce New Fish to Your Home Aquarium 

There is also another article on the possible causes of fish death.   Why did My Fish Die so Fast?
You might want to give it a read if you haven't.

You probably did not acclimate the fish. They could not adapt to the new water in this fashion. Please read the article Thor linked for you. The one on how to introduce new fish to your aquarium. A lot of new fish keepers make the same mistake.

Testing water at this point is quite pointless. While ammonia and nitrite can kill the fish, they do not kill so fast. Died in hours is a sign of shock. It can be easily avoided with proper acclimation.

On the side note, there is no need to take down the fish tank repeatedly. Something in the tank is unlikely the cause, and the fish do not like newly setup fish tank anyway. They like aged water and cycled filter. To help the aquarium nitrogen cycle, you should get a bottle of Tetra SafeStart, but it is something you need to worry about after you get pass the fish acclimation problem.