C02 overdose or just low O2?

[Gerryd]

Hey all,

So I get up this morning and EVERY ONE of the (200+) fish in my 180 were at the surface gasping for 02. The cardinals were very pale and breathing very rapidly. The espei pencils and the platies were also at the surface.

I immediately added a Koralia IV in addition to the Koralia II (which was not running) I have in the tank, and within 15-30 minutes they were settling down. A check 2-3 hours later and only a few fish were lost. All others had the color restored, breathing and swimming normally, normal behavior, etc.

I normally only have the II model powerhead on when c02 is on, and the c02 was OFF at this time.

I still have both powerheads running at this time and will remain that way, I think.....

The tank has been running this way for several weeks now since I replaced the pump and reconfigured the outlet plumbing and I had NEVER seen this prior or any signs of distress at all. I have even massively reduced the c02 bubble rate due to the efficiency of the new setup.

I did my normal 70% weekly water change last night, dosed my N and P and my normal mfg weekly dosage of Excel. Nothing different than any other week, except that I did the WC at 11:00 PM instead of 8-9 PM.

I did not dose more than usual and the fish were fine that I could see when I went to bed 90 minutes later.

The NC canisters were clean, PSI on all 3 guages I have were as they are normally, PH/temp meter showed 'normal' reading for my tank and time of day(recently calibrated), and I had no indications that anything was different in ANY WAY. Current and flow seemed the same as it always was.

Just curious what could have caused this?

Maybe the tap water had more c02 than normal for some reason and it took some time to affect the fish? I did have the normal pearling effect after the WC, but again, no more than normal.

Any thoughts are welcome.

It was really very strange.

 

[Philosophos]

If you bumped an outflow or any source of current, the surface ripple may have decreased. Combine that with a water change, which usually results in a higher water line than before the change, and you have a nice recipe for higher CO2 retention. I witness the change in CO2 quite regularly between water changes in my own tanks.

-Philosophos

 

[Gerryd]

Hi,

Well I don't HAVE a surface ripple when the c02 is off and has been like this for several weeks.

The surface is like glass when the c02 is off and has been for several weeks. Never even saw ONE fish in distress like this, let alone EVERY fish.

I agree that the c02 content can change, but the pct of WC and the amount of fish and all environment parameters SEEMED to be the same.

I am now back to 24/7 ripple as a precautionary measure.

Thanks for the response.

 

[Philosophos]

No surface disturbance at all? I'd guess at low O2 then, unless you're doing wet/dry. Residual CO2 being gassed off at a slow rate won't help either, when combined with respiration.

Now of course none of this explains the change. My guess would be something like a leaky solenoid. Maybe the impeller on a filter wearing out or some other decrease in flow.

On a far longer shot, maybe you filled the water higher, and had some high plant/fish growth making for increased chemical respiration.

Either way, the surface ripple should get rid of the problem.

-Philosophos

 

[Gerryd]

None at the time when c02 is off. No wet/dry but I do have an NC bio canister filled w/bio balls.

C02 solenoid seems fine and the new pump seems fine as well. As stated no APPARENT loss/decrease in flow.

I think I will just send it in to 'Unexplained Mysteries' and always have a surface ripple

Thanks for speculating with me.........

All is well at last check,,,,,,

 

[mr_convitbau]

What is the water temperature? What kind of water conditioner are you using?

I experienced the same problem as yours when I do WC at 86F (Discus tank) using Amquel+ as the conditioner. I lost several cardinal tetras and discus . I did not, however, encounter this problem when doing WC at 78F. I suspected the problem was due to O2 depletion at higher temperature. Less and less gas is able to dissolve in the water when the temp goes up. The phenomenon is like when we boil the water, we see gas coming off and then evaporate. Amquel+ also decreases O2 level in the water for a few hours after the WC.

I then pointed up my filter outlet to create some surface movement. That helped considerably. No more fish loss and gasping at the surface.

I now do so everytime I make a WC. Good luck.

Regards,
TL

 

[rodrigaj]

Your fish are going to get stressed if CO2 increases TOO much overnight or the O2 is reduced TOO much overnight.

Even with high oxygen levels, fish cannot respire CO2 unless the concentration of CO2 in the water is less than the concentration of CO2 in the fishes blood.

With high O2 AND high CO2 in the water, CO2 cannot leave the blood (meaning O2 can't enter the blood) and the animal asphyxiates.

With low O2 AND low CO2 in the water, CO2 can leave the blood but O2 can't enter and the animal asphyxiates.

(I believe George Booth is originally responsible for helping me sort all of this out).

 

[VaughnH]

I lean towards the theory that once the lights go off the plants stop using CO2, so the amount left in the water goes up, and if you run near the maximum allowable amount with the lights on, the amount after the lights go off can be above the allowable amount. I have no proof of this.

I like the idea of good surface rippling 24 hours a day, partly to more rapidly outgas CO2 when the lights go off. And, partly to increase the amount of oxygen in the water at all times. In fact I can't see a good reason to ever have a glassy smooth water surface.

 

[fjf888]

I was in a similar situation about a year ago when I aimed the outflow of my wet dry straight down into the water to eliminate the surface ripple and max out the CO2 during the day. It was fine for many weeks, then one day all my fish were gasping at the surface and pale similar to yours. After that I kept the ripple going and have had not had a problem since.

 

[grayceworks]

I just experienced this last night. I also had my spray bar aimed down into the tank instead of rippling the surface. This was ok before I added the pressurized co2. But yesterday, I added the pressurized co2, and it was nowhere near the yellow range on the drop checker, but it was lighter green than what my diy co2 had been. When I adjusted the spray bar to ripple the surface, all was well.

 

[Tom Barr]

Ripple but not breaking the surface is a good rule of thumb.

Ask this another way:

Would you, if you had no CO2/plants etc, reduce the surface and not have any exchange and turnover?

I do not think so!!!!!!!

So why would you do this with a planted tank?
Conserve CO2?
Have a back up , the plant's production of O2?

1#, you lose a lot of CO2, this can be easily addressed, turn the needle valve another 1/8th turn etc.
2#, what happens if the plants stop growing as well and what happens at night?
No O2 is being produced.

And no O2 is coming in.........

You might get away with things for a while, if the filter gets clogged or slows down, or the plants grow in and you do not prune for a few weeks etc, many things can reduce the flow.



Regards,
Tom Barr