What does 'gasping at surface' look like?

[Bubbles Jackson]

I have a relatively new 120g with (for the first time) CO2 injection.

We're not putting in a huge amount of CO2 (1-2 bubbles/sec). The PH is
pretty low (6ish), due mostly to a large piece of new driftwood (I
think). The filter is an Eheim 2128. There's a lot of plants in the tank.

Anyway, I have seen at least two of the several dalmation mollies at the
surface doing what almost looks like gulping, or blowing bubbles (which
I don't think they do), and as I'm aware that adding too much CO2 can
cause oxygen issues, I'm not sure if it's this "gasping at the surface"
I keep hearing about. I don't think there's rapid gill movement at the
time, and they aren't thrashing around or anything.

After 10 seconds or so, they move back down into the water, and
otherwise seem ok, but I've seen them do it a number of times over the
past week.

None of the other fish are doing this, Rainbows, White Clouds, Cory's,
Harlequins, so I'm not overly concerned, but...

Does this behavior seem familiar to other molly owners, or can somone
describe more clearly what the gasping looks like?


Thanks,

-BJ

[Dinky]

"Bubbles Jackson" > wrote in message
...
> I have a relatively new 120g with (for the first time) CO2 injection.
>
> We're not putting in a huge amount of CO2 (1-2 bubbles/sec). The PH is
> pretty low (6ish), due mostly to a large piece of new driftwood (I
> think). The filter is an Eheim 2128. There's a lot of plants in the
tank.
>
> Anyway, I have seen at least two of the several dalmation mollies at the
> surface doing what almost looks like gulping, or blowing bubbles (which
> I don't think they do), and as I'm aware that adding too much CO2 can
> cause oxygen issues, I'm not sure if it's this "gasping at the surface"
> I keep hearing about. I don't think there's rapid gill movement at the
> time, and they aren't thrashing around or anything.


Mollies are actually a brackish fish, and can even be adjusted to live in a
marine tank, and are accustomed to much higher ph..they're probably a little
stressed.