Mystified by random clown killie disappearance

[confused_aquarist]

Every once in a while my clown killies would completely disappear on me overnight for apparently no reason.
Because these are tiny fish I take caution during water changes to not aspirate them, and also I cover the tank with saran wrap to prevent jumping (but may not always stick completely)
I check the canister filter but it seems they have not been trapped in the filter (also I drill very big holes to lower water flow so I don't think they're stressed by water flow).
I've never had this issue with the lampeye or aphyosemion species I keep in other tanks. The only difference is the clown killie tank has a lot of algae and has a black background.

In the past I made a post about this killie. https://www.fishforums.net/threads/strange-disease-on-clown-killifish.494780/#post-4344035
I had about 22 of them back in Dec. 2014 and now there's only 16, 4 disappeared and 2 lost to jaw/gill rot in Dec 2014 and Feb 2015
The tank still has a lot of algae so it's definitely not the most successful tank I have at the moment, and also some of the fish still have year-long mouth bump problems.
Also notable is the male who jumped has had fin rot issue for a year. The tailfin is pac-man shaped and did not recover at all for the entire year.
I don't have any of these issues with the other killie species so I am completely weirded out. Maybe farm pathogen??

I am not sure what to make of it. Are the disappearances related to algae?? Are the clown killies cannibalistic? They can eat whole dead body overnight? Very confused...
The water is clear with 0 nitrate nitrite/ammonia, near neutral pH and GH 4 KH 1/not black water
Because there is only very few of them I count them everyday; there's no erratic behavior to indicate sickness.

And also concerning is the fact there are no more males in my tank.
I don't want to introduce more fish. Should I be worried about egg-binding, and will unfertilized eggs be eaten or do they rot?

 

[gimme30]

I can't help on the disease front but I've never seen a killie eat a dead tank mate. I assume they're not simply hiding in a heavily scaped tank?

 

[confused_aquarist]

I can't help on the disease front but I've never seen a killie eat a dead tank mate. I assume they're not simply hiding in a heavily scaped tank?

It doesn't seem to be. I've checked every corner and nothing. I didn't think they'd be cannibalistic but this has already happened 4 times! Mysterious.

 

[Back in the fold1]

Snails will eat dead fish and a small fish like your annulatus will be devoured by them unnoticed by you unless you’re looking especially close and often . Also , small fish like these decompose rapidly when they perish . A well established aquarium will have good bacteria that will eat them up really quick , like in two days or so . The only thing you can do is set up a vigil and watch closely to solve your mystery .

 

[confused_aquarist]

I can't help on the

Snails will eat dead fish

Found! In very poor condition indeed!
I haven't done an examination, but in my opinion this is a case of fish tuberculosis, probably the killifish finally came out from a 3 day hiding moments before death to be eaten by birds.
This killifish is only 2 years old.
With this fish tank I have had a history of disease issues, mostly around mouth, gills, and fin.
But the tank was seemingly disease-free for at least a year. Then this happened.
I cannot imagine sudden bacterial outbreak of for example columnaris or aeromonas. The other fish are fine.
So it's likely a chronic condition.
I'm isolating the diseased fish so hopefully it can recover.

Maybe algae played a role in the disease outbreak. Couple of days ago, I cleaned out the filter, and there was a lot of dead algae debris in the filter.
I have tried my best to control the algae, but still, I think it's not very successful in this tank because of poor microbial balance.
I'm not sure if there's anything more I can do.

It's very shocking, because while I have been suspecting fish TB with this tank, I have tried very best to reduce feeding and maintain water quality. Still, it can hit suddenly with no outward sign. I have seen some people keep farm-bred annulatus for over 3 years with disastrous overfeeding, with very bent body shape and swollen stomach. I did not expect this would happen to my fish. Just about a year ago, a big chunk of its tail-fin fell off, and on the same day the killifish was very skittish during feeding but recovered the very next day. The chunk of tail fin never grew back. Ever since then, it has progressively become skinnier day by day.

 

[confused_aquarist]

It's very regrettable because until just a few days ago it was very actively eating, actually I feed so that every fish will get about 1 or 2 0.5mm pellets each day plus a few baby brine maybe 50 or 100 of them, if anything I feel the issue could have been due to starvation. Now it tries to eat baby brine but then just spits.