So I have two ten gallon tanks set up for breeding. Several months ago I did a water change and ran some parameter tests on both of them and within hours afterwards the half dozen Celestial Pearl Danios that I'd had growing out in one of them were dead... the few that I found in their last death throws were gasping on the gravel or hanging among the plants... their fins were ragged with a whitish material. They were all dead by the end of the day, even the few that I tried to resuscitate in a bucket of water from another tank.
The other ten gallon, in which I have some Maculatas was totally unharmed.
After going over it in my mind the only thing that I can think of that went wrong is that I probably got some of the testing solution from my Ammonia or Nitrite test in the tank. I came to this conclusion because although I did all the same stuff to both tanks I performed the tests on the affected tank after I performed the tests on the unaffected tank. My guess is that even though I had rinsed the test tubes in tap water after the first batch of tests there was still some chemicals left in the tubes and when I rinsed them in the tank water (n00b mistake I know, I am ashamed) to perform the second round of test.
As you can imagine I have instated much stricter testing procedures and the test tubes or solution now go no where near my tanks.
After that die off I performed a massive water change and let the tank run for about a month... it has a ton of plants in it and I wanted to see if things would settle out by themselves. Eventually, I put some cherry shrimp in the tank as test pilots. Surprisingly, they did fine and lived in the tank for the next month. They even had babies. I had thought that my troubles were over so I decided to move some of my CPD adults over from another tank to see if things really were back to normal.
Unfortunately, I was wrong. Again, I had a massive die off within hours - the symptoms were the same as before. Also, even though they had lived in the tank for a month or more prior to this, once the fish started to die the shrimp all followed suit.
Current Problem - Disinfecting this tank
Does anyone have any idea what is still going on here?
What is it that is killing my fish? Why were the shrimp okay?
I need to tear the tank down and completely clean it out but how far do you think I should go?
Should I throw out all its contents? The gravel? The plants?
Is their a way to disinfect the sponge?
I'd be okay throwing out the gravel and the plants but I am kind of annoyed at the thought of having to toss the poret sponge for the mattenfilter I have running. Its such a pain to have to order another one.
Anyhow, thank you all very much in advance for you help... I feel like such an idiot and this has been such a setback.