Occasional sudden deaths - shirmps and crabs under suspicion

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Occasional sudden deaths - shirmps and crabs under suspicion

Postby SRThomas » Sat Jun 22, 2013 6:00 pm

Hi All,

For the last month or so, I have had a fish death about once a week. The death occurs suddenly, involving apparently perfectly healthy fish. The fish were: molly (x3), opaline gourami (x2); Bolivian ram (x1 - the most recent (today) and the most annoying, as it was a stunner); guppy (m) (x2). I have also had the following totally disappear: penguin tetra (x4); angel fish (very small; x2) - the tetras disappeared in twos, as did the angels, relatively soon after introduction to the tank.

The tank is a 240l community, planted with wood, fluval 305 and interpet pf1 (both matured). There are lots of hiding spots, so the disappearing fish may have gone in a hole to die as it were. Chemistry is fine (though I plan to do a full test and water change tomorrow - new dog means house has been busy over the last day or so), with weekly water changes of approximately 15-20%. I currently have: opanline gourami x4; Indian gourmai (Trichogaster fasciatus) x2; sailfin molly x1; glass catfish x 2; otocinclus x2; bristlenose plec x2; red fin shark x 1; upside down catfish x1; penguin tetras x5. I also have (and this may be the problem): 2 tropical crabs, and lots of shrimp including one which is more lobster than anything.

Every time there has been a death, it has been a single swift death, with no apparent ill-health (all fish are quarantined for a week beforehand). The dead fish is found being swiftly eaten by the lobster/shrimp.

As a comparison,I have another tank without crabs or lobster-shrimp, which has not seen any such deaths. As such, I think it's the crustaceans which are catching the fish and eating them. Any ideas?

(My plan is to put the prime suspects in isolation,and seeing what happens then, but this will deprive me of my quarantine tank and the other half won't let me get another tank (unless it is a marine for a 'hello fish' (clown fish), which I don't want...).

I plan to get replacements, but my LFS are starting to give me evils...
SRThomas
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Re: Occasional sudden deaths - shirmps and crabs under suspi

Postby Carylnz » Sat Jun 22, 2013 10:07 pm

If you are getting fish from the one source, I would not worry about quarantining them for the time required while you separate the crustaceans. That is the quickest, easiest way to check if they are the culprits.
Otherwise, I would suggest the red tail shark. They often hunt at night. I have no experience with the crustaceans as they are unavailable in my country but they would be my guess.
My home forum is The NZ Fishroom http://www.fnzas.org.nz
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Re: Occasional sudden deaths - shirmps and crabs under suspi

Postby SRThomas » Sun Jun 23, 2013 8:58 am

HI Carolnz,

Thanks for the reply. The possibility that it is the shark has crossed my mind (indeed, having been traumatised by Jaws, I tend to blame sharks for all the evils in the world!). However, this is the second red-tailed shark: the first suffered the same fate (I know I missed this in my original post: i've since checked my records and found that out). Secondly, the first shark was bigger than the current shark (which is only about 5cm long), which, combined with the fact that some of the dead fish have been considerably larger (one of the mollys, a male sailfin, was almost twice the size (taking into account length and bulk), seems to suggest another culprit. Also, from what I can tell, the shark, whilst inquisitive, is not aggressive, and tends to shy away from the more boisterous of the gouramis. A third, and possible clinching reason, why it's probably not the shark is that these fish are found dead after a single night, whilst before they have been in the peak of health. Whilst this is not much on its own (as we know, fish can just drop dead) the consistency of these occurrences, along with the absence of physical evidence of stress or attacks e.g. nipped fins, suggests something other than fish predation (whether long or short term). Also, the fact the otocinclus have not been killed is interesting, bearing in mind their small size and relatively slow moving nature.

What I might do is take your approach, and combine it with my hypothesis, and take out the shark and the larger shrimp and crabs, and put them in my second tank, and putting the fish currently in my second tank (neons, dwarf gourmai pair (M+F), and two small angels) into my larger tank. Whilst this may leave the new additions in danger (if there is a third possible contender for the cause), this may help eliminate either current option (shark.crustaceans).
SRThomas
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Re: Occasional sudden deaths - shirmps and crabs under suspi

Postby SRThomas » Sun Jun 23, 2013 11:45 am

Just thought I should clarify: the shark concerned is a red finned shark, also known as a Ruby Shark (Epalzeorhynchos frenatum). It's not, as my previous posts may have implied, the more obvious culprit for bad behaviour, the red tailed black shark (Epalzeorhynchos bicolor).
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Re: Occasional sudden deaths - shrimps and crabs under suspi

Postby SRThomas » Sun Jun 23, 2013 1:14 pm

And only now I've just realised I've invented a new form of life: the 'shirmp'.... :? Subject name now changed to match reality.
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