Death And A Fishy Smell

[r.w.girard]

So, this afternoon, I found one of my Green Neon Tetras, Paracheirodon simulans, dead and half-eaten under a log, so I fished him out and decided, smelling that the water was off - a little fishy, which should never be the case -, to move my water change up one day.  Taking off the cover to the tank, however, I found two more floating.  So I did my usual partial water change - around 5g in a 20L - and as soon as I had finished my school of tetras came out from hiding in their corner as they are wont to do.  I took the opportunity to count and only was able to find 10, which is down from the 23 that I had last time I counted, a couple of months ago when I did my last rescape.  So I ran off to the store to buy a test kit.  Two years in the hobby and I never have needed one.  This is what the water parameters were as of my return home, after my 25% water change:
 
pH: 6.6
NH3: 0 ppm
NO2: 0 ppm
NO3: 10ppm [it looks a lot more red in the photograph than it really is, but regardless...]
Temp: set to 78*
 
*I don't use a thermometer because the tank can only be warmer than my apartment is - today it was 75º - and if for some reason the temperature had gone up, Green Neons, I read just this morning on SeriouslyFish before seeing the dead fish, can live in water up to 95º.  So I doubt that was the cause.  Plus my other fish should have died as well.
 

 
So projecting back before the water change, nothing could have/should have been particularly high.  And since the pH should have been a little lower before the water change - before degassing the water comes out of my tap with a pH above 7.6 -, there should have been little ammonia in relation to ammonium.
 
But having lost over half of my school, there clearly was clearly some kind of problem.  So I dig deeper.  I had posted not too long ago about my tetras hiding all the time, this despite being in large numbers - even 10, and 13 before today, should have been fairly sufficient as a school - and despite having a densely planted tank with less than 1 watt per gallon of lighting from an old T8.  Further, I have not seen any dead fish before today, nor any symptoms beyond the hiding.  Although I must add that in the morning and during the day, for example during water changes, when the lights are off, they all come out and swim around. Which is exactly what they did today, since I left the light off after the water change.
 
Now, about the conditions in my tank, a couple of weeks ago, my Dwarf Gourami - which also seems to have tumors... - had pop-eye after being punched in the face with science by my male Bolivian Ram. But, as I had read in an article here, it should just clear itself up, if given good water quality.  And, in fact, keeping my normal cleaning schedule, that is exactly what happened.  Also, two weeks ago, I bought nine Otocinclus, of which I have only lost one to date, and that was pretty much immediately.  And, in fact, since adding them, the Green Neon Tetras started being a little less skittish.  Both of these seem to indicate that the water quality is not necessarily the issue being that a) the pop-eye did heal on its own and b) there were very few loses of the newly added and thus naturally at risk Otocinclus.
 
Since they were swimming around today, I did notice two things: one of the fish had a black spot across the lateral stripe of iridophores while another seemed to be swimming at a somewhat odd angle, although it did fine, and was able to flatted itself out, making it hard to tell if it really was unwell.
 
What could it be? I don't know. Violence or predation from the mating pair of Bolivian Rams or from the male Dwarf Gourami would be surprising for me, although possible; at the same time, I am sure it is not the Otocinclus that are killing them!  I'll see what happens tomorrow, if any more do die.  But clearly they have been...

 

[r.w.girard]

Sadly, having posted this, I looked at the tank again and found a fourth fish dead - picture below. Good coloring, looks perfectly healthy.  Healthy and dead.
 

 

[sadguppy]

Do you really have all those fish in a 20l tank as you posted above? If so, that is your answer. Disease spreads very quickly when you are that overstocked and it is super hard to keep water quality good - not just referring to things you can measure but all sorts of poisons, organic build up, minerals and trace elements in the water are harder to keep stable. Neons are very sensitive fish. Even if it is a typo and you meant 20g, it is really too small for over 20 neons let alone the rest of the fish, particularly if the rams are spawning.

Also, I would recommend you get a thermometer. If your heater goes wrong it will kill all your fish and you'll feel very foolish for the sake of a couple of pounds.

 

[TallTree01]

@ sad guppy. I think he means a 20 long. I had a bloke in chat who had a way overstocked ' 20 liter ' but he actually had a 20 gallon long. lol. Either way it is overstocked and you can bet that the rams have nice round bellies fter all those neons.

 

[sadguppy]

Ah, I thought a 20 litre would be too small for the fish to even fit into! One of those UK/US things!

But yes, still on the small side really.

 

[snazy]

Crowded conditions cause not just water quality issues, but stress. Stress leads to disease outbreaks. The fish hiding for so long indicates there was something wrong. Now we are all speculating that the main problem is overcrowding, which is quite possible because 30+ fish in a 20G(if that's the size), is quite a lot, but regardless of that, you'd need to evaluate everything else too considering there are no visual signs of a disease and the water parameters are good at the moment. But keep in mind that you've over 10 fish missing, so that must have caused quite a spike at some stage too, leading to more dying.
The ottos may have brought in something, but then they should have died first I'd think. One of your other fish maybe harassing them to death(fish hiding in a corner...)
Check out for any contaminants that may have possibly entered as well, soapy hands, dirty bucket for water changes, etc...

 

[Lunar Jetman]

Agree with snazy. Perhaps if we knew your set up properly, tank size, inhabitants, cleaning regime, water stats, etc, we might be able to help identify the problem.

 

[r.w.girard]

I have been writing responses for the last hour and a half and yet have succeeded in erasing them all through accidentally scrolling back from the page.  As such, extremely frustrated, I will be brief:
 

1. As a form of measurement, 20L would mean nothing at all: a space is required between the digits and the symbol and "l", not "L", is the preferred SI symbol in all countries using the metric system.
2. The tank in question is a 20L [30"x12"x12"] which is not a 20XH [20"x10"x23"] nor a 20H [24"x12"x16"].
3. Further volume is not the question for stocking such a tank but rather surface area: it would be foolish to think one could stock these three tanks in the same manner, despite their constant volume.
4. The tank is a densely planted 20L with Seachem flourite substrate, a Ehiem 2217 filter at full and heated to 78º - verified overnight by a thermometer - by a Hydor 200 inline heater.
5. The tank before the addition of the nine Otocinclus housed 23 Green Neon Tetras, Paracheirodon simulans, a breeding pair of Bolivian Rams, two Otocinclus and, regrettably, a Dwarf Gourami, counted during my last rescape three months ago.
6. The nine Otocinclus were added with the goal of them being rehomed, at least in part, to another tank.
7. 12 Green Neon tetras were added two years ago and the next 12 six months later.  One died three months ago.
8. The rams have been spawning since introduced into the tank a year and a half ago, with the last spawn a month ago and have been digging pits for their next spawn, although they have yet to clean off a surface.
9. P. simulans, 20 cm is neither P. innesi nor P. axelrodi so unless you say "Green" before "Neon", we are talking about different fish.
10. SeriouslyFish lists the maximum lengths for these species as 20 cm, 30 cm and 35 cm respectively.
11. Thus, a Green Neon Tetra is not simply 30% smaller than a Neon Tetra, and smaller still than a Cardinal Tetra, but rather, assuming proportional dimensions, over three times smaller: 2/3x2/3x2/3 for all dimensions = 8/27 = 0.296.
12. Regardless, I stock my tank to 1" of fish per 12 in2 of surface area, or 30" of fish for a 20L, calculated as follows:
    Green Neon Tera    x 23   x .8"        = 18.4"
    Bolivian Ram           x 2     x 3"         = 6"
    Otocinclus               x 2     x 1.4"      = 2.8"
    Dwarf Gourami        x 1     x 3"         = 3"
                                                             = 30.2"
    
13. The fact that the tank remained stable with this stocking for over a year, before my last rescape, supports my conclusion that overstocking is not the use.
14. I use a cocktail of fertilizers on a variable basis from the Seachem line - Excel is dosed daily - and Tropica Plant Nutrients.
15. I feed a mix of Hikari daphnia, bloodworms and micro pellets, as well as an algae waffer that I break up for the Rams.  Zucchini [courgette] and cucumber are supplemented for the Otocinclus.
16. I change 25% to 50% of the water weekly using dedicated buckets and Seachem Prime declorinator.
17. I don't use any kind of lotion on my hands, so no pollutants from that.
18. In terms of violence, I have witnessed none towards the tetras, even during spawns.
19. Further, as shown in the image in my previous post, there is no wound on the fish, decreasing the likelihood of predation or trauma as cause of death.
20. Likewise, four dead floating in one day would be surprising as well, if predation is the cause as one would assume that they would have been eaten.

Not sure if I am missing anything. If any other information could be helpful, do let me know.


Also, in terms of "hiding," this only started when I removed some Hengel's Rasboras from the same tank.  Until that point, they were far more active. Go figure...

 

[This Old Spouse]

I still can't help but think that overstocking is at the root of this. You lost 13 fish without really noticing, and when they die they release ammonia. The individual spikes could have led to the rest of the deaths. Then you added 9 otos which is another spike. All of this happening in a 20L tank (I have one) is more than I could contemplate not contributing to the deaths. 

 

[phoenixgsd]

my 20L has one male betta, sorry but  i also think your overstocked

 

[r.w.girard]

Please don't take this as me being rude but, to be perfectly honest, I don't particularly care what you think.  Take this as a cautionary tale, if you would like, I don't really mind.
 
I am sure that the number of .5" otocinclus tipped an already precarious scale, as TOS suggested.  One dead fish lead to a couple more.  And that that is that.  But I know that, since adding the otocinclus, until yesterday, only one fish died.  And that was an otocinclus the day after they were added.  How do I know? Because I have been checking for dead fish compulsively for the past two weeks, as one does when adding new fish.  And today was the day that I was going to remove them from the tank so that things could go back to normal.  So my other fish either leap out of the tank and the cat ate them - as has happened before -, or they died while I was away before adding the otocinclus.
 
So again, think whatever you want.  But know this: no matter how you count it, the tank is not currently overstocked.

 

[snazy]

Thinking about the rescape, what exactly did you do? Did you disturb the substrate, or did you replace it?
I changed the substrate in one of my tanks, two months after my fish were sick and several died.

 

[r.w.girard]

You know, I did.  I pulled out all of the planets, gave the gravel a good vacuuming since I only ever clean the open spaces, removed a certain number of MTS that I have been raising with gusto, removed all the older leaves, rearranged the hardscape, added more wood, replanted.  So yea. I definitely upset the substrate.  But still, I just don't get why it is just the GNT that are dying.  Should be the otocinclus.  And that is why I am having such a hard time understand what is happening.
 
That and the fact that I am missing so many without ever having seen a body before now.

 

[snazy]

That's strange. The rest of the fish maybe ate the bodies before you saw them, or your snails? That happens.
Disturbing the substrate may have caused something different than ammonia escape, like hydrogen sulfide maybe.
The other thing that may have happened is lack of oxygen, fish die randomly from that.
Ottos can breathe air so they'll be the least affected. How is your surface movement?
Also, do you add any form of CO2? Maybe carbon dioxide poisoning?

 

[r.w.girard]

It is true that disturbing the substrate could have poisoned the fish but I had put them in a tank with water from the original before disrupting the substrate.  And then I changed the water a whole bunch as it was cloudy and it was only after that that I put the original water back into the tank, with the fish.  Plus I would have smelled the hydrosulfuric acid at some point, since I always have my nose in the tank.  The first dead tetras was not what sent off the sirens for me: it was the smell.  I then found the rest during the water change.
 
As for the rest: I use excel only. And  I keep constant ripples on the top of the tank for gaseous exchange.  But the rams would probably have problems as well, if it were either CO2 poisoning or O2 deficiency.  That and the Dwarf Gourami is rarely at or near the surface ...