Biggest Rainbow Boesemani died after being injured (I think?)

So a few days ago I heard a loud splash and CLANK as a fish jumped against the lid of my tank, I had noticed earlier there had been some fighting between some red boesemani and rainbow boesemani.

The next day I noticed that one side of my 3yr old rainbow boesemani was looking pink and scratched on one side. It looked like it had scrapped against something so I guessed this must have been the fish that jumped against the lid and got injured. It didn't look too bad, some of the scales were damaged, but I thought it would hopefully heal.

This morning I found the said fish dead at the bottom. I looked at all the fish disease and none of the descriptions fit any symptoms I could notice on my fish.

1 month ago I did a filter cleaning and I ended up taking out much more water than I originally intended (like 50% of the water) and i think it destroyed too many beneficial bacterias. I lost an adult cherry barb to dropsy and of the 26 baby cherry barb I had gotten before the filter incident, I think around 10 of them died in the last 2-3 weeks. Since I suspected I probably had cause a cycle reset, I made sure to change 15% of the water every week but it didn't seem to help.

My guess is that the injury + maybe poor quality of the water was enough to finish him off..?
It's quite annoying I've had this tank for 3 years now and I had been doing great for the last year or so without any incident and now my biggest fish is gone = =

 

I’m sorry about your fish. And I don’t think that the water change would have done anything because barely any only like %5 of beneficial bacteria live in the water Column so that wouldn’t have been the issue. And I’m not sure what could have killed your fish if the injury wasn’t to bad and the tank was cycled. Maybe since they were fighting the bully finished him off because he was weak?

 

I’m so sorry about your baby! That’s my worst fear about jumping fish.

 

I’m sorry about your fish. And I don’t think that the water change would have done anything because barely any only like %5 of beneficial bacteria live in the water Column so that wouldn’t have been the issue. And I’m not sure what could have killed your fish if the injury wasn’t to bad and the tank was cycled. Maybe since they were fighting the bully finished him off because he was weak?

The fish really didnt look damaged other than said damage to the scales and the fish was at the bottom, upright looking undisturbed like it just had stopped breathing at some point. I wish I had taken a picture but I looked a several example of disease and it really didnt look anything like what I seen. Also it was the biggest fish in the tank, I thought it was the one bullying the other fish. Can a fish die of fear or something? xD

Can overfeeding cause sudden death? I've been giving them a frozen brine shrimp cube almost everyday lately, I have 30 or so fish, 10 of them being boesemanis while the rest is cherry barb, zebra danio and 3 siamese so that didn't seem too much food to me.

And I didnt know water only had 5% of the bacterias. Then could the 26 new cherrybarb baby I added to the tank bring in a disease?! Didn't have any problem until then... and I don't have space in my appartment to have a quarantine tank. It's my first aquarium but I've been taking care of it for 3 years now and no matter how badly I screwed up, I never had a fish die of dropsy before like my cherry barb.

 

Could it be this little jerk...?
video-1605196265.mp4

He's swimming super fast and seems to be annoying the other fish