Help - New Tank Setup & Death

[rust81]

Hi all - i am new to this forum and am looking for help from those in the know

I have just setup my 2nd tank (50L) which i got 2nd hand. I made sure that this was thoroughly cleaned and then used some baby sterilising fluid to make sure that there were no nasty bacteria in the tank. After doing this i left the tank to dry for 24 hours before adding the new treated water to the tank. I set the heater to 25C and turned the filter on, added 10ml of Stress Zyme (friendly bacteria) and left this for about a week before adding 2 neon tetras. However, after only 1 day both tetras were dead - yet when i checked the levels they came out at:
Ammonia: 0
Nitrite: 0

I removed the dead tetras and left the tank for another week. I reteted the levels and these again came out at 0 for ammonia and nitrite, so i decided to get a hardier species of fish - this time 2 Danios. The first died within the first day, and the remaining danio has died this morning. I have rechecked the levels and there is a small trace of ammonia (0.1 or so), but not enough to kill the fish so quickly.

I really am at a loss as to what is killing them. I presume it must be a water quality problem - but will the readings i am getting it is confusing me. Can anyone help?

 

[Aphotic Phoenix]

What exactly did you clean the tank with?

It's possible that it was contaminated by the "baby sterilizing fluid" since we have no idea what chemicals were in that. There are only a few aquarium safe sterilizers...pure chlorine bleach is one (you have to rinse until you can't smell it anymore, and then rinse some more just to be safe), because chlorine eventually evaporates off.

By the way...adding Stress Zyme and letting the tank sit for a week does nothing. Even IF it contained live bacteria (which most of us doubt), the bacteria would have nothing to feed on without either fish providing ammonia from their waste, or you providing ammonia in a chemical form. There are stickied threads in the "New to the Hobby" section that explain how to properly cycle your tank.

*Edit* If you already have a healthy cycled tank you can take some of the filter media from the old tank and put it in the filter of your new tank to speed the cycle along. Just remember that there must be some food source for the bacteria or they will die.

 

[rust81]

The sterilising fluid i used was Milton - which i think is just chlorine based. After i had emptied the tank i made sure it was completely dry before adding the new water. I guess it's possible that there could have been traces of fluid left - which could be killing the fish. I guess i need to understand whether the water in the tank will be ok once it has cycled - or whether there is something else in there that is harmful to the fish.

I have just done another ammonia reading and this is now 0.25 mg/l - would that be enough to kill the danios?

 

[*Fishkies*]

Did you wash the tank out with water, till it smelled clean, like water?
I would suggest taking the tank and rinsing it out with water a few times.

Also what materials do you have running in your filter? Like carbon?

Your tank may cycle however may not be fine for fish because there could be the trace of chemicals still left in the tank.

 

[-germ-]

Yeah, you need to completely start the tank from scratch,not sure if milton is okay(i would have thought it is), but considering the situation i'd behave like it isn't, clean everything with bleach as described and chuck your filter media, incase this is harbouring any chemical elements...
Then perform a fishless cycle.
Edited for stupidity.