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Re: [APD] Sudden death of all the healthy yamato shrimp

On 6/27/06, Ng Heng Ghee <THGNg at ntu_edu.sg> wrote:
> My new stocking density is:
> - 50 Yamato shrimps
> - 10 Malayan shrimps
> - 15 Cardinal tetra
> - 10 Harlequin tetra
> - 5 Rummy nose tetra

That's a lot of livestock for a 80L.  I have a 70L with 9 neons, 3 yamatos
and a full tank of plants.

After some feeding, I switched off the light at around midnight. Both
> shrimps and fishes look fine and active.
> No distress was observed.

It is likely that your oxygen level was pretty low at that point --
especially if the plants were not in place for a full light cycle -- and
bottomed out during the dark period due to the plants taking up oxygen along
with the fish.  Your test results and solving the problem with surface
agitation all point to oxygen deprivation being the problem.  I have had an
oxygen problem in the past, and I solved it by using a spray bar from a
cannister filter return line that points up towards the surface.  There is
enough current flow at the surface to continually expose fresh water to the
air without so much that I see CO2 being released from the water.  If you
are not adding CO2 then you don't need to worry about too much
surface agitation.

I suggest that you increase the surface agitation via a spray bar or a
powerhead as both will be more efficient than an air stone and the expense
is low.  You will also increase the oxygen content of the water if you leave
the lights on longer -- I do a 10 hour cycle on 2 tanks and a 12 hour cycle
on a 3rd tank.

Sorry you experienced such a heavy loss of livestock.

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