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cuokuo
29th Jun 2013, 01:06 AM
Hi guys,

I'm looking for some advice of what might be causing some RCS issues I've been having. Lately i've been seeing multiple cherrys swarm towards another cherry and eating it alive. The one been eaten is clearly still alive and kicking but must be weakened or something. This is also correlated with a noticeable increase in dying cherries! Other observations include:
1) The ones been attacked have consistently been saddled females (but not berried)
2) The ones attacking mostly seem to be males. I've posted this on another forum and suggestions were it could be related to aggressive mating.
3) Looks like they are actively tearing the victim apart. I got a closeup of one a bit after it was attacked (but still clearly alive adn swimming) and it looks like the part under its thorax had been shredded.
4) Saw the above also happen to a CRS (and I only jsut got them). The CRS had 3-4 males RCSs latched onto it but it managed to shake them and swim away. However I also saw two dead ones so I think its a matter of time before that 3rd one i saw eventually get eaten. This made me think it might not be purely a mating thing since CRSs and RCSs dont mate?

I know they are carnivorous and will eat dead relatives but this is distinctly different since they are actually attacking live ones. The other night i found a couple been attacked, saved them and one pulled out fine and survived okay. Some ideas i have of why this might be happening are:

1) Overcrowding of tank...i only have cherrys and 1 sucker in a 200L tank so they are pretty much the only inhabitants. I estimate there are probably 2000 of them (but thats a very rough guess)
2) Underfeeding (dont think this is it...i feed pretty heavily)
3) Some molting issue. Perhaps the ones been attacked have just molted and are having issues? I think this might be a likely cause because something else i've noticed is molted shells that look like the end of the tail was also shed off. Could be normal but not sure. See the picture below:
https://dl.dropboxusercontent.com/u/1289959/RCS/2013-06-27%2004.32.21.jpg


And the usual list of params:
- 200L tank. heavily planted with lots of moss and cover.
- EI dosing + ada substrate
- Ph is 6.5~6.8 depending on co2 levels during the night
- KH is 3
- GH is since the stupid api kits have a short expiry date on the GH. But from past measruements it shouldnt be higher than 10
- temp 21C


any ideas?

RiverAquatics
23rd Jul 2013, 06:20 AM
pH/temp on the low side but in range, they seem to be breeding well, 2000!

I'm jealous of your temp. and with minor adjusting you're tank would be CRS friendly.

I'd guess you have atypical behaviors because of the population destiny. Shortages in nutrients, maybe, but it might be natural in the sense that there is greater pressure on them with such a large population "mentally" so they become more aggressive, regardless of water quality.

In essence, maybe the population density changes their social behaviors like some other animals. I believe it's known in mammals but not sure about aquaculture. Sometimes known as spatial crowding in biology. As population density changes, behavior adjusts.

I've never had a tank with that density and I have seen some pretty dense populations, perhaps a few larger scale breeders here have tanks with that density and can share their experience.

Regarding mating, possibly too many males wearing her out or a population behavior control. I hope others share a bit on the topic because it is interesting to learn about their behaviors.

If you don't determine the cause and it continues, sell and cull half and see what happens.

cuokuo
24th Aug 2013, 08:54 PM
thanks for the reply RiverAquatics.

what i ended up doing was culling a few hundred males only and the problem went away mostly. There were still a few female deaths here and there afterwards but after 3 weeks away they appear to have stopped that behavior. Still not sure if it was a male/female ratio issue or population density but the culling approach should prove useful for other ppl with the same issues.

hyoushoku
25th Aug 2013, 01:13 AM
Actually my experiences with Neo, when there are too many female shrimps release hormones, the male shrimps will turn into extreme aggressive. End up, they may injure the female. Once the female is injured, they still try to breed with her and at the same time munching off the injured body. I also see them eat away other male's sperm sac that is attached to the female.

I think it is not a good idea to put 2,000 of them in a 200L tank. With 500 of them in my 100L planted shrimp tank (a lot of plants and hiding places), I already observe such behaviour during the "hot mating" season. Maybe you want to consider giving them more hiding places or split them into multiple tank.

Abhishek
29th Aug 2013, 04:32 PM
Overcrowding can be one issue and also mating.

But I have one query -
What are you feeding them?

Noticed this behavior in my shrimps that whenever their diet lacks protein content a less they start cannibalism.
So I mix their diet may be in a week 1-2 with a heavy protein diet and have seen this behavior going down drastically.