I need some help on a distressing mortality situation I encountered a
few days ago. Location is Brisbane.
Tank is 720 litres, Dupla CO2, quite a few plants, filtration by two
1800l/hr Otto canisters, extra surface agitation by Fluval 303 spray
bar.
CO2 gets atomised via a Rio 1700 powerhead and CO2 is on solenoid to pH
meter. Air-curtain at rear of tank on all the time.
No giggling now - this techno-jumble has been pretty stable for some
time ....
NH4 and NO2 are all zero. NO3 - 10-20 ppm pH 6.7-6.8 Temp currently 29C
~ 30C. Summer here.
Water for changes is aged outside in a 200 litre container, dosed with
Prime, agitated by small powerhead
Was doing some maintenance before Xmas - well the 10 day cycle
basically.
(0) 8pm - tank looks good - all fish happily motoring about
(1) Dropped out 200 l of water and replaced from water store at 9pm.
Have done many times before. Fish all still seem happy enough.
(2) Also decided to put Vortex XL diatom filter to shine the water up a
bit for Xmas guests (not that it was that bad or anything - just to
really get every fine particulate). Check everything and lights out.
(3) Anyway next morning - total devastation - something has killed all
my 5 Weipa Running Creek trifasciatas, 6 Bosemanni's,
3 Harvey Ck Blue Eyes, 3 Celebes, 5 Congo tetras, 1 Papuae, 1 large
Bleeding Heart Tetra, 1 large cardinal - all quite large and about a
year old.
large Empire Gudgeon in trouble (and these things are built like little
army-tanks). Dead bodies all over the tank.
Affected fish classes near the surface. I have never seen such
devastation before.
Heartbroken. All these fish have been previously bullet-proof -
surviving all minor diseases that have popped up from time to time
in other fish. All big 3-4 inch fish too. Dead fish have no obvious
marks or symptoms.
(4) But the possible culprit - bloody Precision 9500 airpump failed
during the night - with 2 new rubbers (10 days old) rupturing - cripes
!!
But one Running Ck, one huge Papuae, 2 incisus, a Parkinsonii,
Inornatas, Mucullochi seem OK
Most tetras, Corys, platies, and gouramis are OK and swimming about
normally. Many of the large fish though are dead.
Theories:
Chemical contamination - hard to see how or what ?
Room had a slight stale /rank odour at midnight but I couldn't find a
source (like the tank itself) - thought maybe smell from some water on
the carpet or old socks :-)
or something. But room smells fine again today.
One shop owner said Brisbane chlorine levels are very high at the moment
but I reckon I double dose anyway with Prime so should be OK. Anyway
water aged for 3-4 days normally.
Diatom filter hoses had a slight odour about them (stale old water
internally) - but were well flushed before use. And no diatom powder
didn't cloud the aqaurium - primed in small container.
Pseudomonas or Aeromonas outbreak triggered by water change suggested by
one LFS owner ? Dunno - water looks pretty good today... clear, smells
OK. But anyway maybe an hypothesis worth a thought. Would Octozin treat
this sort of problem - LFS's suggestion ?
Or simply lack of oxygen caused by ruptured air pump and adding 200 l of
water from a relatively sealed drum? (theory maybe low O2 in drum
water). But LFS folks reckon plenty of filtration with other systems as
a counter. Drum has been used a number of times before with no problems
including discus tanks.
CO2 acidosis - well cylinder hasn't dumped - and bubble rate is OK.
Looks same as always. pH/kH/CO2 numbers seem OK to me. I've set pH
controller at 6.9.
So any theories as to how such a prang would have occurred would be
welcome. I'm currently wearing a black-arm band.
Regards & Xmas greetings to all.
Ken