Inexplicable, repeated pH crashes!

I have a 12g NanoCube, with live plants, a very well-functioning
biological filter (no ammonia or nitrites at all, except a tiny spike
when I change water because of the broken-down chloramine--that fades
to 0 in a few hours). I have 5 lively Golden Barbs, and used to have 2
otos, but they eventually died from the pH crashes I'm going to
describe.

For about 4-5 months, I had NO problems with the pH in my tank. Then
suddenly, the pH started drifting down, from 7-7.5 to below 5. The
strangest thing was that the same would be the case after a water
change, where nicely-buffered, pH 7 water would go in, and then within
24 hours it would have drifted steadily down. I would have to add pH
upper (alkaline) to move it back to a stable, around-7 zone.

Actually, the weirdest thing is that when I test the pH (using Tetra's
pH testing liquid), the pH registers at its value after about 5
seconds, but when I leave the vial out, the pH indication steadily
drifts upward, as if there were something in the water (dissolved
CO2?) that was leaving it, and making it steadily more basic. it is
not unusual for it to drift from an initial reading of around 7, to an
eventual reading (about 6-8 hrs later) of 9.

Yesterday, I did a big vacuum-cleaning of the gravel, and took out
tons of this wildly-growing plant (I think a water wisteria), did a
50% water change with properly-buffered pH 7 water....and today, I
noticed two of my Barbs had white, frayed tail fins. Checked the
pH....well below 5. Checked ammonia: zero. Nitrite: zero. Nitrate:
surprisingly close to zero.

WHAT is the source of all this acid? If it's normal nitrification,
then why no nitrates? Why does the pH test steadily drift upward when
the vial is left outside?

I feel like I'm torturing my fish, and not knowing what to do is
driving me nuts.

Please, anyone with advice?

-Jason in Oakland, Calif.

"Jason in Oakland" wrote in message
om...
I have a 12g NanoCube, with live plants, a very well-functioning
biological filter (no ammonia or nitrites at all, except a tiny spike
when I change water because of the broken-down chloramine--that fades
to 0 in a few hours). I have 5 lively Golden Barbs, and used to have 2
otos, but they eventually died from the pH crashes I'm going to
describe.

For about 4-5 months, I had NO problems with the pH in my tank. Then
suddenly, the pH started drifting down, from 7-7.5 to below 5. The
strangest thing was that the same would be the case after a water
change, where nicely-buffered, pH 7 water would go in, and then within
24 hours it would have drifted steadily down. I would have to add pH
upper (alkaline) to move it back to a stable, around-7 zone.

Actually, the weirdest thing is that when I test the pH (using Tetra's
pH testing liquid), the pH registers at its value after about 5
seconds, but when I leave the vial out, the pH indication steadily
drifts upward, as if there were something in the water (dissolved
CO2?) that was leaving it, and making it steadily more basic. it is
not unusual for it to drift from an initial reading of around 7, to an
eventual reading (about 6-8 hrs later) of 9.

Yesterday, I did a big vacuum-cleaning of the gravel, and took out
tons of this wildly-growing plant (I think a water wisteria), did a
50% water change with properly-buffered pH 7 water....and today, I
noticed two of my Barbs had white, frayed tail fins. Checked the
pH....well below 5. Checked ammonia: zero. Nitrite: zero. Nitrate:
surprisingly close to zero.

Test the PH of your tap water after it sits for a few hours.

Test the KH in your tank.

Make certain your PH and Nitrate test kits have not expired.

Add a buffer (carbonate) in the interim if you're worried. Coral, Limestone,
Marble Chips, etc.

WHAT is the source of all this acid? If it's normal nitrification,
then why no nitrates? Why does the pH test steadily drift upward when
the vial is left outside?

I feel like I'm torturing my fish, and not knowing what to do is
driving me nuts.

Please, anyone with advice?

-Jason in Oakland, Calif.

Jason in Oakland wrote:
snip

I think what you need to now is your KH. This is the buffering capacity
of your water. If it's to low, it will result in pH crashes.
To low a KH means 4°

flupke

Thusly (Jason in Oakland) Spake Unto All:

For about 4-5 months, I had NO problems with the pH in my tank. Then
suddenly, the pH started drifting down, from 7-7.5 to below 5.
....
Actually, the weirdest thing is that when I test the pH (using Tetra's
pH testing liquid), the pH registers at its value after about 5
seconds, but when I leave the vial out, the pH indication steadily
drifts upward, as if there were something in the water (dissolved
CO2?) that was leaving it, and making it steadily more basic. it is
not unusual for it to drift from an initial reading of around 7, to an
eventual reading (about 6-8 hrs later) of 9.

1) Place some lime rock decorations or seashells in the tank. That'll
buffer the water to 7.5-7.7, and although limestone reacts slowly,
with sufficient amounts it'll keep pace with whatever is producing
acid or removing bicarbonate.
2) It may be that you're having elevated CO2 levels, especially if
you're adding CO2. Either lowering the addition, or adding an airstone
will take care of that.
3) It could also be, as I said, bicarbonate stripping, by filter
bacteria and plants. Normally that doesn't happen, but with very soft
water it might.
You could dose carbonate/bicarbonate (which is what pH up is) for a
quick fix, and someone will undoubtedly suggest this, but then again,
some limestone in the tank should take care of the problem in a more
controlled, long-term, way.

WHAT is the source of all this acid? If it's normal nitrification,
then why no nitrates? Why does the pH test steadily drift upward when
the vial is left outside?

1) Possibly CO2, the rising pH suggests that. You can check it like
this: take a sample of the pH 5 water, aerate it heavily for an hour,
and take a new pH reading. If the pH has risen appreciably, then CO2
is to blame.
2) Your water is highly, and I mean highly, unlikely to get a pH of 9
from outgassing of CO2 alone. I suspect your pH test is inaccurate by
more than 0.5 units, which also casts some doubt on the accuracy of
the low readings. This inaccuracy *could* be a result of the water
being extremely soft (it is then difficult to measure pH at all, even
with electronic pH meters), or it *could* be a result of the pH
becoming messed-up by the pH up, but I personally have a low opinion
of Tetra brand tests, so if you could get some readings with another
brand of test that would improve at least my confidence in all your pH
readings.

I feel like I'm torturing my fish, and not knowing what to do is
driving me nuts.

Please, anyone with advice?

Decorate with limestone, or put crushed limestone or oolite or coral,
or seashells or cuttlefish bone or eggshell or whatever that's made of
calcium carbonate, in a bag in your filter. Simple as that. You can't
overdose limestone, putting in too much will only "lock" the pH more
securely in the 7.5 - 7.7 (in theory up to 8.3, but in reality 7.7 is
about as high it'll get) range, and putting in too little will still
make your pH drift down more slowly, giving you more time to respond.

However, also do the test for CO2 supersaturation I mentioned. It may
be detrimental for the fish to have very high levels of CO2, but as I
said, if that's the case an airstone will take care of it.