Fish massacre!

[Heimao]

Please help!
I'm so upset-ALL but two of the fish in my large tank died overnight- 8 fish! They were fine yesterday, and this morning I had a pile of dead fish. Only the red guppy and a zebra Dannio survived. Water temp is 74, I do 40% water changes every week. I have a biowheel. The water is clear, and I don't overfeed. The ph is 7 and the nitrites and nitrates are fine. No idea what happened! I want to start over, and need to know how to sterilize the tank, please! One molly did have small red spots. The others didn't. The two I have left are at the top of the tank swimming in place. I have a large bubbler in there, as well.
Thank you!
Heimao

 

[dougall]

How long had the tank been set up?

And how were ammonia readings (An actual reading vs. OK would be best)

 

[Heimao]

I've had the tank set up for 9 months. Don't know the actual reading, I just got "fine" when I got it tested. Getting a kit today. Thanks for replying!!

 

[dougall]

My suspicion would be an ammonia issue potentially, especially if you haven't added new stock in some time.

If you have fish in the water still, it wouldn't hurt to do a bunch of water changes to get any bad levels of anything down and dilute anything/everything. if you do 40% a week, doing that with some frequency now should be fine.

 

[Heimao]

One of my mollies survived! The water is really bad-murky. We just did a 60% water change and it's still murky. He has white spots on him. I think it's ick. How do I sterilize the tank?

 

[dougall]

The need to sterilize the tank would depend on the reason why.

if it's ammonia based, then you shouldn't need to sterilize.

Sterilization shouldn't really be done if you have a living fish though.. It would be better to treat the environment rather than sterilizing and affecting the fish negatively.

 

[fishorama]

There are several ways to treat ich. Salt is 1 way, dyes (methylene blue, Victoria blue), copper (No!, it will make you tank invert unsafe forever! don't do it!)

Keep up large water changes & gravel vacuuming; & retreat to keep optimal dosage of whichever tx you choose. I'm sorry you lost so many fish so fast...I assume you added a new fish recently, that's the only way ich can be introduced & kill like that...it doesn't just magically appear...after 9 months of health?

 

[myswtsins]

With an overnight large die off you really need to ask yourself as many questions as possible, even far fetched ones. Because even if it was an ammonia spike something had to cause it, usually something being introduced.

Nothing stands out, no recent changes? Did you do a water change the day before the deaths? Certain all your equipment is running correctly? At 8:30 the water was clear and by 12 it was really murky and still murky after WC, you sure you got all the dead fish out? Do you use city or well water? No chance a child could have dumped a bunch of food in there or some other not aquarium safe object?

The ich is most likely a side effect of the now bad water and most likely not the cause of the deaths btw.

 

[Fiscian]

What type of substrate?
How deep is the substrate?
Vacuum well weekly?
Murky, what color? Is it white and cloudy or brown murky?

Feed less at once, a few times a day...
Feed only what they can eat in a few minutes with no left-overs...
Feed in the same spot so you can vacuum that area...

 

[Heimao]

thank you!