Fish Gathering at Surface After Power Outage

[Nick Park]

I have a 5-foot 450 litre tank with assorted fish including a bunch of mbuna. It has two filters, an Eheim 2229 and a Fluval FX6.

Yesterday we got hit with blizzards and the power was off for an extended time. I added warm water but many of the fish were looking the worse for wear, probably because of lack of oxygen. I drove through snow drifts to borrow a generator and hooked it up 10 hours into the outage. At that point I got the Eheim up and running (since it has a spray bar), two air stones and the heater.

The fish revived pretty quickly and everything looked OK.

The FX6 was off for 16 hours. I was worried that the bacteria would have died & turned poisonous, so I cleaned the filter out, washing all the sponges & media in tank water and putting new carbon & water polisher in it.

A couple of hours after turning the FX6 on again, the mbuna began gathering at the surface (a parrot fish and a couple of catfish seem unaffected). Since the FX6 seemed to have triggered the problem, I disconnected it and did a 50% water change. But the fish are still all at the surface - all at one corner of the tank.

Ammonia is 0, nitrites are 0 and nitrates are at 40 (so usual parameters). pH and water hardness are normal. Temperature is back to normal (28 centigrade) and water should be oxygenated ok as sprayer and air stones are running properly.

Any advice as to what is happening here? I'm really nervous that I'm going to lose all these fish.

 

[jsodwi]

Lack of O2. Do you have any air stones going?

 

[jsodwi]

Sorry just saw you have air stones in.

 

[xraycer]

I have no idea what's going on either, but at this point, I would just do another water change.

 

[squint]

I wouldn't do another water change. It adds stress and maybe some ammonia and there doesn't appear to be anything to remove.

How cold did it get and how fast did it get back to 28? It may just be that the fish warmed up and need more oxygen while the water warmed up and carries less.

Is the power still out? No carbon monoxide from the generator?

 

[xraycer]

I wouldn't do another water change. It adds stress and maybe some ammonia and there doesn't appear to be anything to remove.

How cold did it get and how fast did it get back to 28? It may just be that the fish warmed up and need more oxygen while the water warmed up and carries less.

Is the power still out? No carbon monoxide from the generator?

These fish looks to be in a desire situation, so stress from a water change isn't go to be that big of a deal.
I would do a water change because it it could be some sort of chemical contamination.
Carbon monoxide doesn't dissolve easily into waterunder normal condition. If there was enough to dissolve into the water, the OP wouldn't be conscious/alive to write this post. Plus, if the water is contaminated with excessive CO, a water change will certainly benefit.

 

[Nick Park]

I wouldn't do another water change. It adds stress and maybe some ammonia and there doesn't appear to be anything to remove.

How cold did it get and how fast did it get back to 28? It may just be that the fish warmed up and need more oxygen while the water warmed up and carries less.

Is the power still out? No carbon monoxide from the generator?

It only dropped to 25.5

Power is back on, thank God. I live in Ireland where the weather is normally mild (if wet). So power outages wouldn't normally be something you plan for. But in the last six months we've had a hurricane and now blizzards with 4 feet of snow.

 

[squint]

These fish looks to be in a desire situation, so stress from a water change isn't go to be that big of a deal.
I would do a water change because it it could be some sort of chemical contamination.
Carbon monoxide doesn't dissolve easily into waterunder normal condition. If there was enough to dissolve into the water, the OP wouldn't be conscious/alive to write this post. Plus, if the water is contaminated with excessive CO, a water change will certainly benefit.

If there's an undesirable gas in water, aeration is much faster.

The additional stress of another water change could put the fish over the edge and we don't even know what we're trying to remove with a water change.

 

[xraycer]

If there's an undesirable gas in water, aeration is much faster.

The additional stress of another water change could put the fish over the edge and we don't even know what we're trying to remove with a water change.

I'm 99.9999% certain its not carbon monoxide that's affecting those fish.

Now, with that major blizzard, bringing all that extra precipitation, perhaps the water suppliers may have significantly increased the disinfectants to the public water supply as a precaution.

 

[squint]

I'm 99.9999% certain its not carbon monoxide that's affecting those fish.

Now, with that major blizzard, bringing all that extra precipitation, perhaps the water suppliers may have significantly increased the disinfectants to the public water supply as a precaution.

In that case, the proper thing to do would be to perform a total chlorine test and add the appropriate amount of dechlorinator. A water change would just add more disinfectant.