No Oxygen

[rabidric]

Well today is a black armband day. We've come down stairs to a tank with most of the fish gasping at the surface and a dead green phantom, dead humphead glass fish and one of our headstanders gone too. I don't understand at all why this has happened - everything was fine when we hit the sack last night. The filters are running and everything seems normal, obviously with dead fish in there the stats are a bit off but not by much so I guess they've not been dead long. We've had power cuts of 5 or 6 hours and no deaths, not recently I'll admit so doubt that has had an effect. So why last night? Could the CO2 system have caused it, that's been in there for ages?

Any ideas??

Massive exam this morning so will have to look later.

We'll miss them.

 

[nurglespuss]

OOOh bad time.

Just put it down to the fact that small enclosed systems are very vulnerable no matter what you do to protect them.

Do you use an air pump at night?

 

[blue acara]

The most likely thing is a co2 overdose I'm afraid. Bad luck loosing those fish.

 

[Spooky76]

That is odd. I have to say, and bear in mind I have never bothered with them....why do you use a c02 system ?
Surely it forces the 02 out of the water ?
All I could suggest is too get an airstone in there, aggitate the water and keep an eye on the stats.

 

[nurglespuss]

CO2 systems are usually used to encourage plant growth, usually at about 4 bubbles per minute.

At night both plants and animals respire (using oxygen) and soo then O2 is depleted.

CO2 has a higher affinity for water than O2 but, and this is the most important part, the dissolved gas carrying capacity of water is trully immense. Your talking litres and litres of gas per small equivilant area of water.

 

[Jonno]

sorry to hear of your news

i have quite a few live plants in my tank - should i have an airstone come on at night or somthing?

 

[nurglespuss]

Only if you have mid-strong CO2 input, or perhaps not much surface agitation (or if the tank is rather warm).

Otherwise, if nothing exhibits any problems theres no real need.

 

[rabidric]

Only if you have mid-strong CO2 input, or perhaps not much surface agitation (or if the tank is rather warm).

Otherwise, if nothing exhibits any problems theres no real need.

Well guys, still gutted - miss them not moving around. The CO2 system was timed to go off at night as were the lights but no we didn't have an air pump in (we do now) but nothing's changed for weeks and never had a problem before. Spoke to the LFS and they said it could be a sudden bacterial bloom, usually happens after a filter clean or major water change. We did do one of the filters and a 15 to 20% water change at the weekend. We never use tap water to clean for obvious reasons and only use RO and dechlorinated water for the change. We use a mix to try and avoid problems. The dechlorinator is for the koi ponds really but we don't use it that often for them - it rains too much!
Something else that we found odd was that the faster bigger fish like silver sharks were unaffected. Experience with koi led us to believe that the bigger fish are the first to suffer.
Anyone else heard of this bacteria bloom thing and if there are any ways of preventing it? Would an air pump have stopped the oxygen depletion?

Cheers

Ric

 

[xxBarneyxx]

What are the other stats (ammonia, nitrite, nitrate, PH and KH).

From what you have discribed I would say it is one fo the below:

Cleaning the filters killed the bacteria and created an ammonia spike:
I never replace bio mdeia or filter pads and always rinse them in tank water only as RO water will kill off bacteria colonies (Though you didnt say you used RO water to clean the filter?).

CO2 malfunction dumped a bunch of CO2 into the tank:
I run my CO2 at 30ppm until the lights go off (about 60 bubbles per minute with my bubble counter) but dont use an airstone at night and there is not a lot of surface movement (spray bar is about 1 inch below the water and creates a slightly ripple in the middle of the tank). CO2 at less then 35-40ppm shouldnt have caused a problem but if your CO2 system messed up this could have gone a lot higher.

I sadly did this years ago with a cheap CO2 system before I knew more about it. Was similar as well in that the clown loaches (which where about 5") where fine but the tetras where all badly effected and I lost a lot of cardinal tetras that where in the tank.

PH crash:
If you are using RO water in the tank you may have lowered the hardness of the water to such a point that the PH is not very well buffered anymore. When the lights went off the plants added CO2 to the water which caused a large swing in the PH of the water and killed the fish. Check your KH and if it is under 4 this could well be the cause. I would recommend a KH of at least 5 to keep a stable PH, lower then this and the PH can be changed very quickly by things like changes in CO2.

You need to check all your water stats to be 100% sure. Even then though if it was an ammonia spike it might have cycled again quickly enough that you wont see any trace of it now.

 

[PRW1988]

CO2 systems are usually used to encourage plant growth, usually at about 4 bubbles per minute.

At night both plants and animals respire (using oxygen) and soo then O2 is depleted.

CO2 has a higher affinity for water than O2 but, and this is the most important part, the dissolved gas carrying capacity of water is trully immense. Your talking litres and litres of gas per small equivilant area of water.

Ummm plants resipre using CO2 and animals with O2, plants give off the O2 and absorb the CO2 that's why they're so important to our enviromnet.

 

[xxBarneyxx]

CO2 systems are usually used to encourage plant growth, usually at about 4 bubbles per minute.

At night both plants and animals respire (using oxygen) and soo then O2 is depleted.

CO2 has a higher affinity for water than O2 but, and this is the most important part, the dissolved gas carrying capacity of water is trully immense. Your talking litres and litres of gas per small equivilant area of water.

Ummm plants resipre using CO2 and animals with O2, plants give off the O2 and absorb the CO2 that's why they're so important to our enviromnet.

Yes, when they photosynthesise. Once the lights go off though they use the O2 and produce CO2.

 

[eschaton]

CO2 systems are usually used to encourage plant growth, usually at about 4 bubbles per minute.

At night both plants and animals respire (using oxygen) and soo then O2 is depleted.

CO2 has a higher affinity for water than O2 but, and this is the most important part, the dissolved gas carrying capacity of water is trully immense. Your talking litres and litres of gas per small equivilant area of water.

Ummm plants resipre using CO2 and animals with O2, plants give off the O2 and absorb the CO2 that's why they're so important to our enviromnet.

Plants only do that during the day when they photosynthesize. At night (or, in the roots), they respire in the exact same way as animals, fungi, or most bacteria.

 

[nurglespuss]

Ummm plants resipre using CO2 and animals with O2, plants give off the O2 and absorb the CO2 that's why they're so important to our enviromnet.

Plants only do that during the day when they photosynthesize. At night (or, in the roots), they respire in the exact same way as animals, fungi, or most bacteria.

lol saved me saying it. But an interesting point here, in school (or at least when I was in school) they only teach about photosynthesis in plants and respiration in animals, like some kind of perfect cycle. Its only later you find out it was a bit of a half truth.

One other thing to consider, which leads me to agree with the idea that CO2 was somehow responsible...

The smaller fish would have succumbed more quickly, as the ammount of O2 hasnt changed, but the concentration of CO2 has theoretically increased, thus affecting smaller volumes mor profoundly. The larger fish would still be able to extract enough O2 from the water (thanks to surface area) and also have a larger holding/transportation capacity for CO2.... an easy way to imagine this is: why did miners take small rodents/birds etc. with them into mines? because the smaller creatures succumb more easily....

Just a thought.

 

[rabidric]

Thanks for all the comments and we'll put words in response to some of them. First, we would never use tap water for cleaning filters and only use water from the tank and only replace media if it's shot - so floss every couple of cleans. We mix RO and dechlorinated in an effort to avoid the possible crash, as I said in an earlier comment. The CO2 system does have pressure guages but we couldn't tell if it had dumped into the tank as the readings are normal. We believe the miners used the small animals as they are more sensitive to poisonous gases (such as coal gas) than us but we could be wrong, often are. Given that we did nothing different than dozens of times before it just seems odd so we'll go for the sudden bacterial growth.

Thanks again for all the comments

Ric