You said later sic "(But doubt it - unless it had a big pulse during the
night - but manometer pressure readings on the Dupla gauge have not
changed - bottle replaced a few days ago)."
Was the bottle changed before or after the wipeout?
If before: When they get low these bottles can give the gauges fits (from
what I read on the plant list). Perhaps you wouldn't see the complete
emptying of your bottle (you would still see pressure, but now of a gas
instead of the CO2 liquid). Maybe you experienced "near end of the bottle
dump" that still left pressure in the bottle. By the morning the <dumped>
CO2 had gone away (pH back to normal, 6.7-6.8) but most were sufficated by
CO2. I don't think it's the pH drop that get's them in a deluge of CO2 but
rather the lack of O2. The fact that the airpump failed and you might have
had a partial CO2 dump could have worked enough to kill your fish but not be
readily detectable. The normal levels of CO2 that you were adding though
(without the airstones/pump working) would not have been enough to do the
damage. Plant dudes know that the extra O2 put into the system BEFORE the
lights go out by the plants really offsets any respiration that the plants
do during the Calvin dark cycle. There are a great many hobbyists that use
CO2 and do not use much of an offgassing system in their tanks (day or night
use). I don't think that the failure of the airpump could have been the
main problem. High temps didn't help dissolved O2 values either.
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.
Have to agree on the comments on ammonia not being the major killer. A
large amount would still be measureable in the tank. As a native of St.
Louis I consider myself and my local aquarium club to be "experts" on
dealing with chloramines and feel that a few comments are in order. We have
been dealing with chloramines with our "Mighty Mississippi" (and Missouri
River) water for some 25 years now. While I won't doubt that people used to
chlorine in their system experienced massive fish kills when they were
switched over to chloramines we have been dealing with it for years with
VERY FEW problems. This is one of the "myths of the hobby" that I see being
repeated again. You can simply double or triple dose with sodium
thiosulfate and it will break the bond. If the chlorine removal product has
any real reducing/chemical power, then a 3x dose will break your chlorine
bond. If you like, measure the ammonia level from a bucket of such water.
It will be higher than what you would normally have in your tank BUT if you
have any sort of biological filter what-so-ever it will not be measurable in
short order. Unless you bleached :-) your filters during the cleaning
process your biological filters would have sucked up the ammonia from the
<broken> chloramines in no time.
If you doubt your source of chlorine remover you can always make your own.
3 tablespoons (my tablespoon says = 15 ml) to a final volume of 100 ml. Use
hot water and shake it up. If you have water harder than ~ 125 ppm use RO
or distilled water. 2 drops per gallon will break the chloramine. I have
been know to add three or 4/gallon (can't count) without any ill effects on
the fish. Higher amounts will yield a sulphury smell.
**A watchout - even homemade stuff can cause problems. You often get this
from photography supply houses. One time I got some that had something else
in it that killed fish. There are lots of chemicals in the photography
hobby that even mixed in small amounts could kill your fish. So I test with
<cichlids> when getting a new batch of sodium thiosulfate crystals. Also
you can't beat Amquel or Novaqua for convenience. The gallon size usually
means I'll always have some on hand.
Ammonia readings - When using "chloramine neutralizing products" such as
Amquel, Nessler's reagent will give false positives. It also reacts with a
lot of amine type buffers but those reactions are so extreme that the kits
will tell you that your fish should be very dead! Kordon (Amquel) says to
use Salicylate test kits (spelling that always gives me a headache so I need
to find an aspirin now). I didn't see that cross reactivity that Seachem
promised that you would see when I used a Salicylate based kit. I would
take their information with a grain of salicylic acid. Might be time to go
buy a new ammonia test kit. Naturally avoid Nessler kits. The Tetra kit is
a reasonable one at least in my hands.
Is there a possibility that you forgot to add Prime/dechlor to your barrel
before treating your tank? I would like to tell you that I've never done
this but I have with horrible results. From your email you performed about
a 30% (200/700L) change. I was routinely doing a 30-50% change. Probably
was a 70-80% mortality with everyone else gasping at the surface, some 40
adults in a 100 gallon refrigerator liner. Was doing a late nite water
change and after filling went to bed. So the distress of the fish, which
would have normally been immediately noticed went unchecked. Could the
batch of Prime suddenly go bad? I can't really see how that would work. If
you were doing the same water changes 10 days ago you should have seen some
suggestion that the product wasn't working. I now fill my water barrels and
attempt to have a fail safe mechanism in place. Hoses are unhooked that
will prevent me from pumping water into my tanks. When dechlor is added
then system is reset. If you didn't have a pop with the gas tank I will bet
that it was the failure to add dechlor. This really sounds like the same
situation that I ran through. (fish were really slimy the next morning).
Chloramines will be removed with carbon but if you believe like most plant
dudes then you don't have any. Old carbon wouldn't be of much help. If you
haven't done any more water changes then your fish could still be feeling
the effects of chloramine. (I had tested it positive for 10+ days in an
open bucket). Any ammonia problems will be much easier to deal with at a
lower pH so putting the CO2 back on line (?pH now 7.6) to lower back to 6.8
would probably help. But add plenty of airstones for nighttime gas off
until fish have totally recovered.
Plague??? Did you add any new fish to the tank in the last week? If not if
you have another tank with a "test type fish that was affected" drop it into
the tank and see if it too becomes greatly stressed.
sorry for your losses. Hope the new millenium will be better.
Gary Lange
gwlange at STLNET.com