Dissolved oxygen disaster

[simon_the_plant_nerd]

We had a disaster yesterday. My partner came running to tell me that our fish were all right at the surface of the water, most of them upside down. I ran in to find all of our fish at the surface gasping.

I immediately realised this was an oxygen issue. However, everything at first inspection was working. Filter was running with surface agitation happening. Airstone running as usual. CO2 drop checker was green, although perhaps a little more lime green than usual.

Carried out two 50% water changes immediately. I had done a water change on Sunday. I didn’t test the water before removing it as I was in a hurry to solve the problem so I tested the water in the bucket once I had started refilling.

All test results good although the pH was off the scale low. This seems like a CO2 problem and one which happened incredibly quickly. CO2 is now off and will stay off until I can remove it and test the regulator in a controlled environment away from my fish.

My tetras, corys and bristlenose were all fine within 10-15 minutes of the water change. Sadly, one of my fish didn’t recover. Based on this I’m seriously reconsidering if I want to continue CO2 in the tank.

I thought about posting some photos however they may be distressing so have decided not to.

 

[PARAGUAY]

Sorry to hear this, I think you have done the right thing, stopping CO2 at least while you check what went wrong

 

[MoFish]

Is it possible you had an end of tank dump on your CO2 cannister? What kind of CO2 set up do you have?

 

[Ibz10]

Just reading your post @simon_the_plant_nerd and I have had the exact same thing happen to me at approx the exact same time/day 🤯 spooky. I carried out a water change at 3am in the morning and then again during the day. All water parameters were normal for me and I have also removed my C02 for now (although im not sure its a C02 issue for me). Fortunately I did not have any fish loss and dont know how I would deal with it if I did as I keep quite a few rare parotocinclus species. I will continue water changes, let us know how you are getting on.

 

[G H Nelson]

I had done a water change on Sunday

What conditioner did you use?

 

[dw1305]

Hi all,

My tetras, corys and bristlenose were all fine within 10-15 minutes of the water change.

Well done, that sounds very much <"like it was excess CO2">.

Because haemoglobin transports both gases elevated CO2 levels in the water mean less haemoglobin is available for oxygen transport. Have a look at the Bohr-Root Effect <"ph/c02 discovery that dont quite understand">

Based on this I’m seriously reconsidering if I want to continue CO2 in the tank.

It is <"the major reason"> why I wouldn't consider using CO2 myself - <"CO2 Disaster">.

cheers Darrel

 

[Connswater]

thought about posting some photos however they may be distressing so have decided not to

Good call there.
My experience is that the end of tank dump happens rarely but it is always possible especially with single control regulators. I once had one of these near misses and it so 'put the wind up me' I ran a good sized 3 foot tank (20 inches front to back) for over a year on 24 hour a day yeast and sugar generated CO2, worked a treat actually, in terms of plants and fish, but it is bother and eventually I got fed up with refilling the system when summer meant I had to do so weekly.

 

[simon_the_plant_nerd]

Is it possible you had an end of tank dump on your CO2 cannister? What kind of CO2 set up do you have?

The cylinder is probably about half full at the moment. I use a fire extinguisher with a CO2 Supermarket single stage regulator. The regulator is a few years old now and almost certainly out of warranty. I haven’t got the cylinder out and weighed it but it’s a fairly new one and the regulator is holding the output pressure. I’m able to increase and decrease the pressure turning the regulator knob.

The culprit appears to be the needle valve. I disconnected the CO2 from the tank and turned the solenoid on. The bubble counter looked like a shook up bottle of lemonade.

I have a small green mark on the needle valve knob to mark its position and it was lined up. It’s not a perfect system as the body of the regulator can be moved and the line would be out of place but the needle valve in the same position. I’m aware of this though and the body is pointing in the usual direction so I don’t think it’s been moved.

I was able to close the needle valve fully and stop the flow of CO2 and open it up again slowly to achieve a normal flow rate. I’ve since turned if off again. I’ll do a long term test at the weekend and leave it running in a bucket for some time.

So, either the needle valve has gone faulty, which I guess is possible but maybe not likely. Or the valve was opened by accident. I do have a small child who fiddles with everything however this door has a child lock on it and my partner says he hasn’t been near it.

I could have knocked the valve when I was doing maintenance but the issue occurred two days later (did the water change Sunday morning and this happened Tuesday afternoon) and the flow of CO2 was very high when I turned it on today.

That CO2 regulator will not be used on a tank with livestock again. Maybe I’ll risk it on a plant only system if it tests out okay but not on a tank with fish.

What conditioner did you use?

I use the Blagdon pond one. I’ve been using it for years without issue.

 

[simon_the_plant_nerd]

Good call there.

I didn’t want someone to open a thread and get a shock. However if anyone thinks they would learn something from seeing the effect too much CO2 can have on their fish, whether to recognise the signs or to just put into perspective the risk, I am able to share a picture privately.

 

[simon_the_plant_nerd]

Just reading your post @simon_the_plant_nerd and I have had the exact same thing happen to me at approx the exact same time/day 🤯 spooky. I carried out a water change at 3am in the morning and then again during the day. All water parameters were normal for me and I have also removed my C02 for now (although im not sure its a C02 issue for me). Fortunately I did not have any fish loss and dont know how I would deal with it if I did as I keep quite a few rare parotocinclus species. I will continue water changes, let us know how you are getting on.

How is your tank doing now?

 

[Ibz10]

How is your tank doing now?

I did another water change and all seems well now, im still not sure what caused the oxygen depletion and dont feel convinced it was just the C02 (although my c02 canister had fallen on its side). I will do 1 more large water change. Is it possible to send me some pictures you took so I can compare with mine?

My body is suffering from the range of mixed emotions, anxious thoughts and feelings but all worth it to keep fish safe and healthy.