Help Emergency- Fish Die Off

Pete Des

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EMERGENCY: fish died off (beginner here)
possible issue 1.
Did I kill my live rock? To kill GHA, I dipped it park hydrogen peroxide (maybe 10 percent) and 90 percent water. I took that and put it a bucket of tank water to swish it around. All but 3 fish died yesterday. So, is all the beneficial bacteria gone? and the rock is pointless? But that was like 3-4 weeks ago
possible issue 2
to lower phosphates and nitrates, I dosed Phosphate-E and NoPox according to the directions. About 3 hours later I noticed my fish start to die.
Possible issue 3
I just added a picasso trigger to the tank (very passive guy). didn't touch my corals or even my shrimp
I'm in panic mode
Possible issue 4
I set up a macro algae reactor the day before the fish died.


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Hi. Sorry you are having issues. What size is your tank and how long has it been set up? What are your current parameters?

1. I never dipped with any kind of peroxide I always used tank water I would increase the salinity of, so I can’t speak to that method but it seems harsh in my mind. So definitely a possible issue. It’s hard to totally “kill” live rock though unless it was bad live rock to start, so if you only dipped it and didn’t soak it in peroxide solution it might not be a lost cause.

2. I use phosguard and filter media to lower phosphates, skimmer ofcourse also, using chemicals could have depleted the oxygen in the tank considerably. I’d make sure you have good agitation right now.

3. How’s the Picasso doing? You do any water changes after losing fish?

4. I can’t help you here. Never used one myself but I can’t imagine why it would be the problem.

Hang in there. Hopefully others will weigh in.


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3 years
I would say the double dose of chemicals from option 2 is the most likely culprit. Did you aI'm your powerheads up at the surface of the water to help with oxygen? Option 1 is unlikely given the time frame. It is possible the picasso trigger is killing the other fish, but the timing and what is being killed seems odd. What size is your tank though? Picasso Triggers need very large tanks (ie 200-300 gallons). Option 4 is the least likely of any of them. Unless you have a bunch of dead macroalgae producing ammonia it wouldn't be the cause of this problem.

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