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RCS disappearing without a trace!

Nat N

Nat N

Member
Joined
28 Dec 2011
Messages
120
Hi all,
I have been successfully keeping planted aquariums for a while but I am new on this forum - and coming in with a puzzle.
I hope somebody can shed some light on this. I have a very successful little low tech tank, denseley planted. It now happenned for the second time and I am really puzzled by this. A thriving population of RCS dissapeared without a trace - e.g. no dead bodies whatsoever. Both times the population is growing, seems to be happy with plenty of them out and about and small young shrimps seen literally in dozens everywhere - and then I see fewer and fewer of them within a couple of weeks. I have not seen any dead shrimps and everything within the tank is the same as previously...
Tank stats:
30 litres (24 litres of water)
PH - 7.4
KH - 6
GH - 9
Phosphates - 1.5 ppm
Nitrates - 10 ppm
Filtration is with an external smallest Hydor with glassware and the temp is about 20 C.
Plants: Crypt Beckettii, Pogostemon Helferi, Eleocharis Parvula, Cardamine Lyrata, Arthraxon (Sphaerocaryum Malacense) - which replaced Cyperus about 6 weeks ago and recently added Hydrocotyle Sibthorpioides.
Light - 24 watts
Ferts - mostly none, an occasional dose of a pre-mixed off the shelf one every few weeks with half a dose.
Other inhabitants: 5 White Cloud Mountain Minnows, two Amanos and one Sewellia sp.
Any thoughts?
Thanks in advance.
 
When I re-started the colony last May, I added about 40-50 shrimps from different sources. In July I had so many babies there that a dozen of shrimp from this tank were transferred to another one to start a new colony there. By September this tank was literally "bursting" with shrimps - adults and juveniles. They were everywhere in great numbers. By mid December there is almost none left: I could see 4 after half an hour searching. As I said, I never saw any dead shripms. The fish in the tank are the same for the whole time. The shrimps are fed with Hikari Shrimp Cousine, granular spirulina, occasional little bit of crushed sinking tablet and whatever food drops down which the fish do not catch.
By the way, the "daughter" colony in another tank is doing well - living with Threadfin Rainbows and Harlequin Rasboras - there are many many of the shrimps seen around....
 
Could be that they are getting sucked into the filter and pasted, could be the minnows, most likely a combination of the 2?
 
I also suspect that the Minnows might be to blame. However, the fact that the shrimps were multiplying and thriving first puzzles me. When I re-started the colony last May, I added about 40-50 shrimps from different sources. In July I had so many babies there that a dozen of shrimp from this tank were transferred to another one to start a new colony there. By September this tank was literally "bursting" with shrimps - adults and juveniles. They were everywhere in great numbers. By mid December there is almost none left: I could see 4 after half an hour searching. As I said, I never saw any dead shripms. The fish in the tank are the same for the whole time.
I know about the filter: I kept on finding baby shrimps in there - all alive and well. I did change the intake of the filter and now they do not get sucked in there.
By the way, the "daughter" colony in another tank is doing well - living with Threadfin Rainbows and Harlequin Rasboras - there are many many of the shrimps seen around.... I never heard about Minnows being a threat to the shrimps (at least not to adults which are three quaters of the size of the Minnows).
I did another seach on the internet... nope... nothing about Minnows eating adult shrimps... Honestly, I cannot think of anything else...
 
Minnows are big enough to eat the babies and maybe the juvies but won't be able to manage the adults. Even then if you've got enough hiding places in the form of moss etc the babies should be mainly safe to grow.


Nat N said:
When I re-started the colony last May, I added about 40-50 shrimps from different sources. In July I had so many babies there that a dozen of shrimp from this tank were transferred to another one to start a new colony there. By September this tank was literally "bursting" with shrimps - adults and juveniles. They were everywhere in great numbers
Click to expand...

Paradoxically it may be that your initial breeding success is the cause via a bacterial bloom. I've seen it happen in other nanos. There is an unsaid assumption that shrimp don't add to the bioload but of course they do if there are enough of them. When there's too many waste will build up and result in pathogens. Have had this problem myself and now am very on the case in controlling the population in my nano.

First step may be seachem paraguard to knock out the bacteria.
 
You know what? I think that your suggestion about the bacterial bloom is the correct one! I myself did not quite belive that Amanos and/or Minnows may ever contribute that much into the death of the colony. The suggestion about some pathogens accumulating when big numbers of shrimps live in a relatively small tank is definately a much more likely cause of events - and this is the first time somebody actually mentioned this. Thanks.
In any case, I decided that the Amanos will go into one of my other tanks to join a small group already living there and the Minnows will probably be given to a good home for free (this is ONLY if I find a suitable home for them). And the tank will be re-populated with the likes of Emerald Eye Rasbora or such - and a new colony of RCS. Thanks for the tip about Seachem Paraguard as well.
 
Hi everyone,
I thought I would post an update to share the experience. So far, I rehomed my Minnows. A very nice chap came to collect and he already has a set up dedicated to them, so I am sure they would be in good hands. I introduced Galaxy Rasboras (Danio Margaritatus to be correct). Imediately, I noticed my remaining RCS out and about (I did not know if I had any left at all!). So, a thing to note - Minnows seem to be preditory or at least intimidating for RCS... Another update to follow in a week or so...
 
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