[0xDEADBEEF]

A while ago I had a guppy population explosion in my Neon Tetra/Otocinclus (20 neons, 7 Otos, 1 Dwarf Puffer, and at one point 100+ guppies in 30G, I know, crazy) tank which I finally solved by catching all the guppies and giving them to an owner of an Oscar.
So now we are at more reasonable 20 neons + 7 otos + Dwarf Puffer snail policeman.
I have caught all the guppies at night, and changed water afterwards.
Neons definitely got stressed because they acted skittish for next two days. Otos, well, they are always skittish, and Puffer doesn't care.

But now, my Neons are dying one by one. So far I lost 4.
Found one drifitng by the filter intake. Next day, another one dead close to surface. Another day and another one was isolated from the school and later dying barely swimming in weird position. So I fished it out and noticed half eaten and rotten another one on the bottom.

The first one had maybe some missing scales or colorless patch on the side but that could be from other fish bitting it after it died. 2nd one bulging belly but maybe it started rotting already. The one that died when I was watching looked perfectly normal and I have performet autopsy afterwards cutting few cross sections. The meat looked nice and firm, guts, well, like guts, maybe little too soft.

So I don't know, is it NTD? I would expect it to show more externally and internally. Or is it the stress from the guppy hunt a week ago? Or they are overeating now because they don't have to compete for food with guppies?
Or stress triggered susceptibility to NTD or other disease?

Any idea what to treat this with? I usually add some Melafix and Tantora Catappa extract after each water change.

Oh, and I didn't know Neons would eat their own dead.

 

[WaterLife]

Neon Tetra Disease will typically have fish with white patches on their body, usually under the dorsal fin (saddle back). Or at their peduncle (base of tail), but could possibly be anywhere. Usually the white patch is present. Deformed spines may occur.

Read here for more info
Neon Tetra & FNT Disease; Sporozoan Fish Infection

If at least the white patches are not present, I would doubt it's NTD. NTD is said to have no known cure. Columnaris can have similar traits, and that is curable. It can be brought on from weakened fish (opportunistic)

When you were chasing around all the guppies, did you disturb the substrate a lot?

First step is to check your water parameters to rule that out.


Just reasoning it out, Neons did get stressed from you chasing and catching all the guppies. With the guppies not there, they might feel there is no dither fish (even though they pretty much are dither fish), which would result in them being in more fear/stress. And from the last negative experience with your presence, I am sure you are not seen as a friendly figure (so you are a cause of fear/stress currently). Group fish can sense stress in the other fish, and with other fish dying, things can go downhill (water quality wise too, which makes things even worse). Neons aren't the bravest fish, so they do stress out easier than many fish. But I have seen stressed out neons a lot. They don't always just drop like flies because of stress though. If it is stress, minimize it by keeping lights off, provide more hiding areas, and maybe even limit your presence too them until they settle down (though you do need to inspect them every so often for any possible disease progression. Stressed fish have a compromised immune system, so they do become more susceptible to disease they were previously unaffected by.

How long have you had the neons?

So check your water parameters and then examine the fish and note any symptoms they show.
Currently, just not enough info to give a disease ID (the description of dead fish isn't very reliable).

You some kind of surgeon or something? I've yet to dissect a fish myself (besides fish meant for consumption)

By the way, most fish will eat a dead fish, even their own kind.

 

[0xDEADBEEF]

When you were chasing around all the guppies, did you disturb the substrate a lot?

Yeah, it was unavoidable, but I did change water afterwards, I will try another water change and vacuuming substrate when I will find some time.

If it is stress, minimize it by keeping lights off, provide more hiding areas, and maybe even limit your presence too them until they settle down (though you do need to inspect them every so often for any possible disease progression.

The tank is in the garage so I do not go there that often, feed them twice a day and occasional comings and goings by the car. It is heavily planted (e.g. the plants are out of control ;-)) so they do have ton of hiding space.

Stressed fish have a compromised immune system, so they do become more susceptible to disease they were previously unaffected by.

Thats what I suspect.

How long have you had the neons?

The tank was started in summer 2015. Neons dropped in soon afterwards, so about half a year. Initially a bunch of them died because it was super hot and I had to buy a chiller for the tank. Then things were awesome until one day I bought two guppy females for my 3G tank on my desk at work.

You some kind of surgeon or something? I've yet to dissect a fish myself (besides fish meant for consumption)

LOL, no, but cutting little dead Neon with Xacto blade is much easier and less mess than cleaning guts of a big fish you caught in the lake (I used to fish as a kid, and my dad was like: you caught it, you clean it).

water params (api test strips)
GH (ppm) 30
KH (ppm) 40
pH 7.5
NO2 (ppm) 0
NO3 (ppm) 20
Temp: 26 deg C (controlled with heater and chiller)

Damn, lost 2 more today. One is too rotten to tell. The other, even dead looks like model from Neon Tetra Swimsuit Magazine, no external signs of any disease. WTH?
I dosed with ParaGuard today and tried to install UV sterilized but it is of course little bit too tall to fit in my tank.
Few more days and the problem will solve itself. There will be no Neons left.

So does anyone SF Bay Area want free Super UP-23 13 UV sterilizer in? Just come and pick it up.