New fish died in hours and cycling ?

[jen626]

Hi, I used to be on here a lot when I had goldfish and I know a bit about cycling and stuff.  My 11 year old former daycare kid wanted to start a tank, originally wanted goldfish but I talked her into tropicals since it was a 10 gallon tank set up.  So we got everything together and set it up and added 2 black skirt tetras.  They died within 6 hours (I was only there when they were added). We temp matched but did not check the pH so I'm guessing the pH was too different or there was a contaminant in the tank.  We did rinse everything (gravel/tank/filter media/deco etc.) One thing that could have contaminated is that she reached in the water with a scrunchie on her wrist.

After the deaths they did a 50% water change.  They got two more black skirts, temp matched the water and same thing, they lived like 5 hours.  So again I'm thinking pH or contamination?  Fish from the tank at the store were all fine over the next few days. 

So now I suggested that they cycle the tank prior to getting any more fish even though I that wasn't the problem. They bought some beneficial bacteria balls and put them in and I told them to put a little tiny pinch of fish food in everyday, does that sound right? It's been a long time since I have done this!

I plan to check the water once a week to see how the cycle is going.

Parameters at death:

Water not tested (so maybe pH was too different) 

10 gallon tank, Whisper 20i filter (without charcoal) , heater at 78, treated with Prime, gravel and fake plants, air bubbler as a decoration.  Not sure what the fish were doing before they died.

Just wondering if you had any ideas why else they might have died and also if using the beneficial bacteria balls along with putting a little bit of food in each day should work forgetting the tank cycled. I have freshwater API Master Test drops that I can check the water with before we add fish and to see if it is cycled.

Thanks for any help!

Edited May 24, 2021 by jen626
Clarity

[koko]

Well the first thing I would do is test the water. Get a test kit and test the ammonia, nitrites, nitrates Ph and Kh.

Is the tank near anything that could harm them. Say like cleaning stuff or air spray, perfume things like that?