Fish gasping within 1-2 hours

[ltsai]

Having trouble recently with my co2. It was stable for a week until I found them at the water surface.

Did an immediate water change and raised my outtake to break the water surface.

I had been trying to tune down the needle valve for the past few days, until it was closed and I didn't realized that. Waited for a few hours and nothing happened... Silly me.

There was once that within 30 mins, they are all up there. Currently, it takes 2 hours but my drop checker is still blue-green and I have strong rippling. The needle valve is almost 1/3 of my original setting that was working fine for the past week or so. I can no longer see the mist unless I stare at it very hard.

I have yet measure the amount of co2 using the inverted cup method.

The corys are fine though but I see my oto going up to take a gulp of air. The H. Rasboras are always at the water surface. Mollies and guppies are up there too.

How should I troubleshoot this? Could it be the fine mist from my UP inline atomizer been causing the problem? Should I shift it to my intake instead of outtake?

This is a 60x30x30cm tank with a 1200l/h canister filter with moderate planting. Using an UP A-165 regulator and UP inline atomizer.

 

[ceg4048]

Sound like a distribution problem. You have not described or shown how your flow is distributed.

You should also sample the pH over time to see what is happening in the water with the dissolution.

Cheers,

 

[ltsai]

I gassed out the remainder of the co2 by putting in a sponge filter for a day. The PH dropped from 7 to 5 within an hour or less. I might have turned it too high this time. Going to tune it down further and test again.

 

[ltsai]

Here's a picture of the outlet. It is pointing 45 degrees from bottom right to top left. About 2 inches below water surface and slightly pointing up.

 

[ltsai]

Managed to redo the tests today.

+0hr: 7
+1hr: 6.5
+2hr: 6
+7hr: 6

The fish are no longer gasping at the top.