disaster..

[InDeathsEmbrace]

Was reading about the death of marc vivien foe on my way home.Got the biggest shock of my life when tragedy struck in my very own tank when i got home.i went home to a tankful of dead fish.They were ok in the morning when being fed...when i got back some were gasping at the surface,swimming on their sides but most were lying at the bottom motionless.even prawns....i had to pick up all the bodies with chopsticks and tweezers.Worst of all i don't even know what happened.
measured ph:7 kH:5 NO2:<0.3
bought some feeder catfish put 3 in some tankwater they died within a minute.
Anyway im at a lost at what to do now...don't know how to get rid of the carcasses inside the dense foilage.

[Goondoo]

new tank?
test for NH3(Ammonia) and NO2(Nitrite).
If don't have, go buy those sets from LFS.

[PeterGwee]

What kind of CO2 system are you using? DIY or pressurised? NO2 is at < 0.3....Is your bioload high? How about your plant load? If your pH and KH is what it seems to be, you are on the low side...with plants growing well, you should not detect any form of NO2 as ammonia would have been taken up so fast that non would make it to NO2. The solution now is to do a large water change and fine tune your CO2 properly. Get a pH test pen or monitor...they are worth the money as compared to a cheap pH test kit which lacks precision. Once the CO2 is fixed, the plants should pick up and water conditions would improve. Healthy plants healthy fish.

[David]

Did you introduce anything new into your tank like liquid fert or medication and do you have UV filter on at the same time?

[vinz]

Ummm... actually any NH3/4/NO2/NO3 you measure now could well be from the dead carcasses.

CO2 dump from your cylinder? Any new fishes/water change recently? Oh, and check if anyone in the house sprayed insecticide/other chemicals in the room.

[lvanilla]

Your senario is quite servre.Did u hav a power failure? When there is power failure, yr filter will stop, co2 will continue to inject, lamps will be off.... If this is too long, filter bacteria will die and foul.. this will kill the fishes n shrimps when power up. Noramlly after a long power failure, U hav to wash yr filter and change water. How to know whether u hav power failure, juz look at yr timer if u hav any. It will be slower.Hope this helps.

[InDeathsEmbrace]

nope no power failure no addition of anything either..
plants are doing quite well alot of bubbling when i returned so i ruled out lack of oxygen.
anyway nothing much i can do now...just did a 50% water change.
tomorrow going to clean out the filter..
then filter over abit of carbon for a week,change water every few days...then i hope everything returns to normal,after which i can introduce fish again after 2 wks.
I set up my tank 6 months ago already..was thinking of getting more expensive fish like discus but don't think i can do that anymore.
lucky for me the 20+ fish which perished were cardinals,SAe,ottos,pencils,rasboras..not too big a loss financially

[limsteel]

carp... my home have a schedule power shut down on the 7 July for 1 hrs... but is it really 1 hrs?

I have to take leave liao!

[vinz]

Lim, a planted tank can take a few hours power off, no problem as long your tank's fish-load is not overloaded.

InDeathsEmbrace, errr... lack of oxygen and CO2 overdose are two different things. CO2 poisoning can happen when there is too much CO2 in the water whether oxygen is sufficient or not. Search the web for 'carbon dioxide poisoning' or 'CO2 poisoning' to find out more.

[Allen_1971]

I agree... Just cuz your plants are bubbling does not rule out CO2 poisoning.

From what I understand, fishes rely on a process of osmosis to exchange CO2 in their body with the water. If your CO2 levels are too high, this exchange is inhibited. Basically what results is that their CO2 levels accumulate, and then acidosis sets in. This eventually which kills the buggers. The reason why lots of them gasp at the surface is not because there is more O2 there, but because the CO2 loss at the surface is higher. The only fishes which would be more immune to this would be labyrinth fishes which are able to handle ambient air.

Having said this, some catfishes are labyrinth fishes... so if the ones you put in are, then its unlikely to be due to CO2 toxicity.

Your NO2 is a suspicion. at 0.3, its a bit high. Its possible that what you measured could be caused by the dead fishes itself, but I'm guessing its not. I'm actually guessing that something you did upset the biological balance leading to a NO2 buildup. The symptoms of which are very similar to what you described as well. Some examples are introducing new fishes (1-2 weeks back), CO2 depletion with high bioload, or cleaning your filter media. All of these could lead to a buildup of NO2.