Anyone know what this fish died of?

[Mama Karoti]

I got home tonight and found one of my red eye tetras floating dead. I have no idea what happened, and I was hoping maybe someone on here has seen something like this before and can shed light on it. I have only been fish keeping for a year and haven't experienced much fish death.

I take a head count every night when I feed. Last night everyone was active, eating, and appeared normal. This morning I don't know because my lights were off.

I have only ever euthanized a fish and lost two without a trace, never found one dead like this. I don't know if the red discoloration is normal for a dead fish or if she suffered some sort of trauma. It definitely wasn't there last night.

Everybody else seems fine tonight.

Water parameters:
Ammonia = 0
Nitrite = 0
Nitrate = 20

60 gallon heavily planted with:
1 female pearl gourami
2 platies
7 neon tetras
4 false julii cories
2 SAE's (4")
2 juvenile albino BN
3 otos
5 red eye tetras (was 6)

I have two aquaclear 70 HOBs + circulation pump.

Weekly PWC of 33% (20 gallons). Last water change one week ago.

What's changed?
Started dosing daily potassium and phosphate and Plantex from Greenleaf Aquariums about a week ago per their instructions. Dose 10 ml Excel daily.

Removed a bunch of floating hornwort last night that was unhealthy and left a few healthy stems.

Added otos two weeks ago (active and eating)

My gourami likes the hornwort. Is it possible that she was upset and attacked my tetra? Am I reaching here? She doesn't appear aggressive other than occasionally chasing a platy off, but who knows what happens at night.



Sent from my iPhone using Aquarium Advice

 

[Mama Karoti]

I turned the lights on this morning and did a head count. Everyone seems ok this morning, knock on wood. Going to continue to monitor closely and do a pwc tonight.


Sent from my iPhone using Aquarium Advice

 

[Fishfur]

Fish sometimes die for no apparent reason. If it is only one, just watch to be sure it isn't the start of something nasty. Fish, like most animals, try to hide it if they are unwell, it is a survival instinct. So we dont necessarily see much in the way of symptoms.