Harlequins Keep Dying

ferg42995

I have a planted community tank. Started cycling in early October. It was very well cycled and has remained in perfect condition since. I added fish beginning in early December. Every single fish has lived -- other than my Harlequin Rasboras. I buy them, and then they die off one by one. Then I buy more, and they die. Everyone else lives just fine. I am giving up on them and not buying anymore because apparently it is bad luck for Harlequins to be owned by me! Anyone else ever have problems like this with their Harlequins? I thought they were supposed to be super hardy but they are the only fish I can't get to live.
 

Ling313

Have you tested your water parameters recently? Also, who are the tank mates? They may be non-compatible
 
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ferg42995

Have you tested your water parameters recently? Also, who are the tank mates? They may be non-compatible
Tankmates are:
1 Golden Mystery Snail
1 Zebra Nerite Snail
6 Ember Tetras
4 Harlequin Rasboras (now)
4 Endler Livebearers
4 False Juli Corydoras
6 or 7 Emerald Dwarf Rasboras
5 Bloodfin Tetras
4 Amano Shrimp
2 Peacock Gudgeons
1 Bolivian Ram

Plants are:
Italian Vallisnaria
Anacharis
Cryptocoryne Lutea

pH 7.0
Ammonia 0
Nitrite 0
Nitrate 5

I do weekly water changes around 40%. I feed twice a day what the fish eat in 2 minutes. The diet varies greatly with frozen, flake, pellets, etc.

Tank is 44g tall pentagon. 55g Tidal Filter HOB, plus an air stone and an Aquarium Co-Op Medium sponge filter.

All of the other fish have lived fine without issue. But these, I buy them and they slowly die off. I buy more and they slowly die off. Everyone else is happy as a clam. So strange.
 
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MacZ

It sometimes happens that a pathogen only kills off one species for no apparent reason. If you have bought new harlequins twice and the phenomenon keeps going, leave the rest be and just keep them without restocking. If need be let them go extinct, as rehoming might be unfairly introducing a species specific disease to somebody else's tank.

Otherwise just try to optimize conditions, up the waterchanges, add leaves and alder cones, maybe add more plants or change the layout more to their needs. That's probably all that you can do.
 
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ferg42995

It sometimes happens that a pathogen only kills off one species for no apparent reason. If you have bought new harlequins twice and the phenomenon keeps going, leave the rest be and just keep them without restocking. If need be let them go extinct, as rehoming might be unfairly introducing a species specific disease to somebody else's tank.

Otherwise just try to optimize conditions, up the waterchanges, add leaves and alder cones, maybe add more plants or change the layout more to their needs. That's probably all that you can do.
That makes sense that maybe it is a weird species only pathogen. I agree about not restocking them. We have decided that we would not as it seems to be they don't do well for us. And I agree about not rehoming them. I would hate to cause harm to someone's tank. I will look at adding more plants for sure. That was something I was already wanting to do anyway. This just gives me an excuse to do it sooner! Thanks for insight.
 
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MacZ

You're welcome. If you need tank optimizing, just open a thread, bet people here are eager to help.
 
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CTYankee79

Just curious are the harlequins juveniles or very tiny when you’ve been adding them? I had the same problem with mine and it took about 3 restocks to get it where I wanted it (I have about 22). What I finally figured out was that I was over feeding them—because they were so tiny they couldn’t handle how much food I was giving them. I noticed it was always the small ones that would die. They are all bigger now and hardy as can be.

I’m sure it’s more likely what Macz said but just wanted to offer my experience with them..
 
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ferg42995

Just curious are the harlequins juveniles or very tiny when you’ve been adding them? I had the same problem with mine and it took about 3 restocks to get it where I wanted it (I have about 22). What I finally figured out was that I was over feeding them—because they were so tiny they couldn’t handle how much food I was giving them. I noticed it was always the small ones that would die. They are all bigger now and hardy as can be.

I’m sure it’s more likely what Macz said but just wanted to offer my experience with them..
That's interesting and a possibility. They are juveniles when I get them. I'm not sure how to feed them less as they are in the tank with everyone else. I might could try getting some and putting them in the QT tank so I could manage their food intake a bit better. If they live there for a month or two and grow big enough, then move them to the main tank. I'll have to decide if they are worth that experiment or if we should move on to something different. But they are beautiful so......
 
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CTYankee79

That's interesting and a possibility. They are juveniles when I get them. I'm not sure how to feed them less as they are in the tank with everyone else. I might could try getting some and putting them in the QT tank so I could manage their food intake a bit better. If they live there for a month or two and grow big enough, then move them to the main tank. I'll have to decide if they are worth that experiment or if we should move on to something different. But they are beautiful so......
That’s a good idea. I struggled with the same thing, trying to feed a community tank but not over feed them. Let me know if you end up doing that I’m curious if it will prevent them from dying.

They are really beautiful...a big school all colored up in a planted tank is very pretty
 
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Cherryshrimp420

Seems like you are feeding too much for the tank to handle. My harlequins each eat 1-2 grains of Omega One pellet per day. More feeding = more poop = worse water quality
 
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MacZ

Seems like you are feeding too much for the tank to handle. My harlequins each eat 1-2 grains of Omega One pellet per day. More feeding = more poop = worse water quality

If that was the case here there would likely be more than just one species affected.
 
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Cherryshrimp420

If that was the case here there would likely be more than just one species affected.

Yeah that's true but just going by his info his tank's stocking is pretty high and feeding amount is pretty large too. I wouldn't point the issue to some specific disease yet without addressing the fundamentals which is just water quality.
 
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MacZ

That's for sure not wrong, but the phenomenon of just one species dyeing off is quite common independently of hygiene. Not everything boils down to this.
 
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ferg42995

Thank you both, for your input. I actually have really good water parameters and with the deaths only being the same species, while I may indeed be overfeeding (I don't know), I don't think that is causing the problem as far as water quality goes. I have clean parameters and weekly water changes have kept it that way thus far.
 
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Cherryshrimp420

That's for sure not wrong, but the phenomenon of just one species dyeing off is quite common independently of hygiene. Not everything boils down to this.

He has harlequins still living in his tank...so it seems to me highly unlikely that his tank harlequins has some specific disease that LFS harlequins have no protection against. Species-only pathogen is such a crazy and rare phenomenon and it really only applies to genetically identical populations like extremely in-bred bettas, self-cloning species etc. For Harlequins I don't think this is the right direction that we should be going....

Thank you both, for your input. I actually have really good water parameters and with the deaths only being the same species, while I may indeed be overfeeding (I don't know), I don't think that is causing the problem as far as water quality goes. I have clean parameters and weekly water changes have kept it that way thus far.

What do you mean by good parameters? Ammonia, nitrite, nitrate is just a useful indicator and not the complete story to a water's quality. Other things like dissolved organic matter is more directly linked to bacteria growth than ammonia, nitrite, nitrates. But these things are not easily testable so the easiest way for a hobbyist to address these issues is to simply feed less.
 
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MacZ

He has harlequins still living in his tank...so it seems to me highly unlikely that his tank harlequins has some specific disease that LFS harlequins have no protection against. Species-only pathogen is such a crazy and rare phenomenon and it really only applies to genetically identical populations like extremely in-bred bettas, self-cloning species etc. For Harlequins I don't think this is the right direction that we should be going....

I respectfully disagree, but your arguments are still valid. I've seen the phenomenon often enough, but I'll let you gladly try and find out what else it could be in this case.
 
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