sad day for my fish tank.. did i mess up?

[vertner82]

Ok so to start off I have a 120 gallon tank with a fx5 filter. The tank mates are 11 3-5 inch piranha.

I changed 20% of the water last week.

Last night i did three things

1st I fed the fish talapia filet. I had fed them some of this very filet before. I had just thawed it out in the fridge. it had been in the fridge for two days now.

2nd I took the bubbler out of my tank i did some reading on the net that led me to believe that maybe i had to much oxygen for my plants to grow at a good rate. took this out at 2AM.

3rd I changed out the light fixture to two small ones and doing that i had to remount the blue led strip light (it was mounted to my four foot fixture but i took that out) it was late so i just zip tied it to the center support beam on the tank. apparently i let it dangle in the water on one end... It is suppose to be ok to submergable.

Ok here is the sad part i did all of this and the fish looked ok It was 2am in the morning. I went to bed then i woke up this morning (7:30AM) to the fish hitting the top of the water which is unusual. so i go out to see what is going on and i see 3 maybe four fish dead and the rest floating upside down half alive. There was also a bunch of white balls on the bottom of the fish tank.

After a few min of pure panic i figured that the white balls on the bottom of the fish tank was the fish that i had fed them. the water also had a terrible smell to it.

Fisrt response was to put the buble bar back in. second was to get all of the fish food out of the tank. Third was to immediately do a water changed (25%). I ended up saving five of the eleven.

I checked the water quality while i was puting water back in the tank. here is how they went:
Nitrate 15-30
nitrite 0
ph 6.5 -7
kh 0
gh 160ish
water temp was 79

Im not sure what caused this to happen. if you have any helpful thoughts would be nice. I didn't know fish could throw up the food i gave them i have never seen this before. maybe the fish was bad that i feed them. any advice would be nice. maybe the bubler did it i have done this in the past and it didn't hurt them( i was having a filter issue). Im not sure what i did except i killed my fish somehow...

Thanks in advance

 

[Wroberson]

I have some opinion on part of your issue.

You said you removed the bubbler and early morning or late at night you saw some of your fish near the water line.

I've read that at night, plants release CO2. Add to this less oxygen due to removing the bubbler. The fishmay had become acclimated to high oxygen and may have been suffocating and trying to get more Oxygen.

I have seen my turquoise rainbow fish do this almost every night. They only do it at night. They may be playing with the reflections, they may just be shoaling. No one has ever dies, but the first thing I thought about seeing this is that plants do release CO2 at night.

 

[brennae]

IMO it was the fish. thawed fish has to be eaten immediately and you said it was thawed for 2 days which leads me to think it went bad, also the smell makes me think this too. I had a tragedy once with some African Clawed Frogs. I got some plants and used some fertilizer and it killed 5 out of 6 frogs. I was really upset as I had the frogs about 10 years. Sorry for your loss!

 

[shellieca]

What was your ammonia level? I would lean towards the frozen fish you fed them being spoiled & possibly causing an ammonia spike as it sat in the tank. When I feed frozen foods I have a glass or something that I put tank water in & thaw the food in then feed immediately. I am a little surprised that if the fish was spoiled you didn't see any of them spitting it out when you fed them initially. Do you watch them for a few minutes when you feed them? I personally would do a larger water change of 50%+ to be on the safe side.

 

[melbaby45]

black mold or algea