Mysterious Deaths?

[noelsfishland]

Maybe it was the silicone you used I always thought that you had to use aquarium grade so it does not give of any toxins,It could be the anti mold stuff that in the silicone that is causing the problem

 

[letstalkfish]

Usually when I have started up all my tanks. Like my 100 gallon I took 50% from my already cycled 120. I gravel some of the poop when I was transferring the water to my 100 to help with the cycle. Then I took the filter off my 120 and put it on the 100g. Let it run for 2-3 days then I added a couple of goldfish and left them in there for about 2-3 days. If they're doing fine I added a couple of fish. Wait another week, add a couple of more fish and so on. What I am think is you added to many fish at once and had a spike. That's why I usually add fish slow and wait.

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Again, adding water from an existing tank does not help at all with the cycle - if anything it is bad, all you are transferring is nitrate. Additionally, "gravel vac-ing" some of the poop in has an adverse effect as well. I haven't read past page two in the thread, but it sounds like the tank either wasn't rinsed enough after using the rubbing alcohol, or the silicone is what is doing it.

EDIT: Sounds like you narrowed it down to be silicon, most likely. I just read the whole adding water and fish poo thing and had to comment prematurely.