Sudden Multiple Fish Death - Help

[rosshind]

Sudden Multiple fish death - HELP

30 litre tank

NH3/4: 0.3 mg/l
NO2 : 0.1 mg/l
NO3 : 1 mg/l
PO4 : 2 mg/l
pH : 6.8
deg C: 25
deg F 78
Stocking:The tank is stocked with 7, 3cm fish and 3 snails.
2inch sand bed

I have Danio's a minnow, and 3 guppies and two tiny fry. Yesterday morning I did a routine 30% water change. Last night I noticed that the activity of the fish had slowed a little, they had moved towards the surface. They didn't seem to be gasping but the snails had moved to the waterline. My zebra danio was swimming / floating upside down, all other fish were upright and swiming fine. I watched it, and it was dead within about 10 minutes. I discovered it had some redness around its gills. All the params i've measured are fairly stable and have been for months, I therefore suspected unknown poisoning, I did a 60% urgent water change, taking all the usual precautions (dechlorination / ensuring temperature was ok).

This morning I found another danio dead and one of the fry in its death throws. I have a fluval 2 filter , which I installed two days ago. the venturi valve on the filter seems to work fine - plenty of bubbles, and I have been keeping up with water changes. I would be surprised if disolved oxygen concentration was the problem, but I'm getting a test for that today. Are the symptoms consistent with that? How so after I've done those water changes, if that was a problem, wouldnt it take a while to depleat the o2 in the tank? Might electrical discharge form the filter be acause, or bacterial infection - does that come on so suddenly?

The're dropping like flies, can anyone help before the rest of them die? Are thse symptoms familliar. Thre is no fungus / parasites / white spot or anyhting visible. They are perfect (a bit slower than normal) one minute, then on their backs the next , dead 10 minutes later...


Any ideas people ?

Thanks everyone, it's gutting when they die!

 

[Miss Wiggle]

the ammonia and nitrite is a big worry, when you put the new filter on did you put the old media into it or start from fresh?

 

[rosshind]

the ammonia and nitrite is a big worry, when you put the new filter on did you put the old media into it or start from fresh?

Those levels are extreemly low. 0.3ppm of ammonia shouldn't harm something like a zebra dannio, or much else in a tropical tank for that matter, same goes for the nitrite. Ideally they would be zero, I admit it. Those dannios can survive fine in water in excess of 6ppm ammonia. They are documented as particularly good cyclers.. hmmm.... Do you think the symptoms are consistent with ammonia poisoning? Maybe the test is out of date... My girlfriend is taking a sample to the lfs this lunch time to get them to test the ammonia too. I have a fine sand bed with a huge surface area for nitrifying bacteria. It's always worked fine.

If my tests are accurate, I don't think cycling is the problem.. Big if. Why do you think such small ammounts are a problem?

Any other ideas.. thanks for your help by the way.

 

[Miss Wiggle]

sorry but any level of ammonia is avery bad sign.

when you put the new filter on did you use media from the old one?

 

[vinylman]

Yup, the only safe levels of ammonia and nitrites for fish are zero. As Miss Wiggle asked: did you just swap filters, or did you take the media out of the old one and put it in the new?.

 

[rosshind]

The reason there is a small level of ammonia according to the test is
that the two guppies were recently added to the community.
In the normal course of running any aquarium this can cause small,
temporary fluctuations in NH / N02 level. This is due to a lag in
the colonisation rates of nitrosomonas and nitrobacter bacteria.
They need time to expand in number to metabolise the extra ammonia produced by the new additions.
These fluctuations are to be expected to be small (this one is) and should be monitored.
Ammonia levels of 0.3ppm are tiny and do not kill zebra dannios.
I have seen them exist (in someone elses tank) for several weeks at a time at levels of 6ppm and above (i.e. off the scale). They have a reputation as excellent cyclers, this is well documented.

To answer your question, yes, the old filter media was added as a
precaution, but it is not the main area of colonisation for the nitrifying bacteria in this particular set up.

Someone mentioned that the substrate was not the main area of colonisation for nitrifying bacteria.
This is entirely dependant on the surface area to valume ratio of the substrate involved. Small grains = higher ratio
therefore more bacteria. The reason your filter media is fuzzy and spongey is in order to increase the surface area to volume ratio. Small grains do something similar.
I certainly don't shun filter media as a viable alternative though, it is after all designed for the purpose
I could refer you to some references about this, but I do not have any to hand. I would be very interested to read your evidence to the contrary. I have had sucess with the sand bed method for many years. My NH levels are never more than 0 without a reason

The issue here is not one of cycling. You are barking up the wrong tree I think, but thanks very much indeed for your help. A discussion on cycling would be great. But ideally on another topic.

Can anyone suggest anything else. Mystery disease or 02 depletion. I'm getting an o2 test tonight.

Ross.

 

[poopsydrew]

The reason there is a small level of ammonia according to the test is
that the two guppies were recently added to the community.
In the normal course of running any aquarium this can cause small,
temporary fluctuations in NH / N02 level. This is due to a lag in
the colonisation rates of nitrosomonas and nitrobacter bacteria.
They need time to expand in number to metabolise the extra ammonia produced by the new additions.
These fluctuations are to be expected to be small (this one is) and should be monitored.
Ammonia levels of 0.3ppm are tiny and do not kill zebra dannios.
I have seen them exist (in someone elses tank) for several weeks at a time at levels of 6ppm and above (i.e. off the scale). They have a reputation as excellent cyclers, this is well documented.

To answer your question, yes, the old filter media was added as a
precaution, but it is not the main area of colonisation for the nitrifying bacteria in this particular set up.

Someone mentioned that the substrate was not the main area of colonisation for nitrifying bacteria.
This is entirely dependant on the surface area to valume ratio of the substrate involved. Small grains = higher ratio
therefore more bacteria. The reason your filter media is fuzzy and spongey is in order to increase the surface area to volume ratio. Small grains do something similar.
I certainly don't shun filter media as a viable alternative though, it is after all designed for the purpose
I could refer you to some references about this, but I do not have any to hand. I would be very interested to read your evidence to the contrary. I have had sucess with the sand bed method for many years. My NH levels are never more than 0 without a reason

The issue here is not one of cycling. You are barking up the wrong tree I think, but thanks very much indeed for your help. A discussion on cycling would be great. But ideally on another topic.

Can anyone suggest anything else. Mystery disease or 02 depletion. I'm getting an o2 test tonight.

Ross.

Well that was very matter of fact, hmm how about......i dont know.....Your tank is cycling.

 

[Xebadir]

Sorry, but your argument with regards to substrate is faulty: Nitrifying bacteria require O2 to function: This exists in filtration systems as the movement generated allows more O2 into the water, thus allowing the nitryfiying bacteria to propagate and do their job. Substrate is at the lowest part of your tank, and thus the most distant from the O2 source: hence the smallest concerntration of bacteria are present within it.

Prolonged exposure to even low ammonia reading burns the gills of your fish: try pouring bleach down your nose and see how it feels(i dont really mean try this but you get the idea). This weakens the fish making them either succeptible to infection or succumbing to oxygen starvation.

You can pull out the bible for all its worth: but i will guarantee you the symptoms presenting(redness of the gills), suggest a burning by ammonia: your tank is cycling because you didnt do a media transfer. I would be quite happy to prove the exact reasons for this, after I sit an exam tommorow. Your fish are basically suffocating: People on here have vast experience and have likely been through your situation: while reading theory is great, practical exp. far outweighs this.

Goodluck.

 

[Amunet]

Your fish are dying b/c your tank is still cycling.
ANY amount of ammonia & nitrites can and will kill your fish.
Just b/c danios are known to be hardy good cycling fish doesn't mean they're not going to be affected by these in the water.
I can tell you this for a fact b/c we had danios at first. Were using them to help us cycle our tank.
I did water changes every day to every other day to keep readings as low as possible and guess what... they all died anyway.

I'd do a few water changes just to see if some clean water will help your fish.