Malawi tank disaster

[GuardedResponse]

Just had a massive die off in my Malawi tank (36*18*12"). Everything seemed
fine about 6PM, at 12AM I had 10 dead fish - 6 yellow labs and 4 crabros.
Tested the water and it looks like my filters crashed for some reason,
nitrite was at 15ppm. This tank is triple filtered with a cannister filter
(with prefilter) doing biological duties and 2 fluval 3 internal power
filters doing biological / mechanical duties. I carry out a 40% water change
weekly and give the internal filter and cannister pre-filter a clean in tank
water at the same time. Apart from the Crabros and labs the tank contains:
1* 6" plec
2* 4" Pseudotropheus (sp)
2* 2" unidentified from a mixed malawi tank at local LFS
a pair of Kribs
a small 3" synodontis.

The above all survived.

I know this is a big load for the tank size, but it has been running for
over a year without a single death and all the fish appeared healthy.

I have done an 80% water change / gravel vac. Removed the 2 internal filters
and replaced with yet another mature fluval 3 from a different tank. Removed
all the media from the cannister and replaced with 50 % mature from another
filter and 50% new. With the much reduced fish load I'm hoping this will be
sufficient to return the tank to a cycled status very quickly. I've also
dosed the tank with melafix and esha 2000 ( a broad spectrum treatment).

Tank furniture is Tuffa rock and a couple of pieces of bog wood, all in
there since I started the tank up.

So...... any ideas what caused the nitrite spike and why my filters didn't
handle it?

Are Labs and Crabros more sensitive to nitrites than the other fish in the
tank?

What else should I do?

Oh, one other thing. A couple of days ago I was feeding frozen bloodworm to
some of my other tanks (all of which are fine) and, without thinking dropped
a cube into the Malawi tank. I normally never feed bloodworm in this tank.

The dead fish were all beautiful adults of 4" plus that I had since they
were just over an inch or so.

This has left me quite upset and feeling that I have failed in my 'duty of
care'

Water parameters are (normally) PH 7.4, Nitrate 25 mg/l, Nitrite 0, kh 17d,
and gh 17d ( I use multi - test strips)
Any help or advice appreciated.

Thanks, GR

[Rick]

"GuardedResponse" > wrote in message
...
> Just had a massive die off in my Malawi tank (36*18*12"). Everything
seemed
> fine about 6PM, at 12AM I had 10 dead fish - 6 yellow labs and 4 crabros.
> Tested the water and it looks like my filters crashed for some reason,
> nitrite was at 15ppm. This tank is triple filtered with a cannister filter
> (with prefilter) doing biological duties and 2 fluval 3 internal power
> filters doing biological / mechanical duties. I carry out a 40% water
change
> weekly and give the internal filter and cannister pre-filter a clean in
tank
> water at the same time. Apart from the Crabros and labs the tank contains:
> 1* 6" plec
> 2* 4" Pseudotropheus (sp)
> 2* 2" unidentified from a mixed malawi tank at local LFS
> a pair of Kribs
> a small 3" synodontis.
>
> The above all survived.
>
> I know this is a big load for the tank size, but it has been running for
> over a year without a single death and all the fish appeared healthy.
>
> I have done an 80% water change / gravel vac. Removed the 2 internal
filters
> and replaced with yet another mature fluval 3 from a different tank.
Removed
> all the media from the cannister and replaced with 50 % mature from
another
> filter and 50% new. With the much reduced fish load I'm hoping this will
be
> sufficient to return the tank to a cycled status very quickly. I've also
> dosed the tank with melafix and esha 2000 ( a broad spectrum treatment).
>
> Tank furniture is Tuffa rock and a couple of pieces of bog wood, all in
> there since I started the tank up.
>
> So...... any ideas what caused the nitrite spike and why my filters didn't
> handle it?
>
> Are Labs and Crabros more sensitive to nitrites than the other fish in the
> tank?
>
> What else should I do?
>
> Oh, one other thing. A couple of days ago I was feeding frozen bloodworm
to
> some of my other tanks (all of which are fine) and, without thinking
dropped
> a cube into the Malawi tank. I normally never feed bloodworm in this tank.
>
> The dead fish were all beautiful adults of 4" plus that I had since they
> were just over an inch or so.
>
> This has left me quite upset and feeling that I have failed in my 'duty of
> care'
>
> Water parameters are (normally) PH 7.4, Nitrate 25 mg/l, Nitrite 0, kh
17d,
> and gh 17d ( I use multi - test strips)
> Any help or advice appreciated.
>
> Thanks, GR
>
>

I feed my Mbunas frozen blood worms on occasion, they love them, just don't
over do it. What do you mean your filters "crashed". I have inadvertently
forgot to plug two filters back in on a 33g tank one time. They were out for
two days before I realized it and I lost 8 of 12 Tiger Barbs and the rest
developed Ich. Your PH may be fine for your fish . I prefer to keep my
Malawi's around 8. If the filters were out for awhile then that is going to
cause a nitrite spike and your levels are likely responsible for the die
off. Sorry about the losses.

Rick

[Mark Trueman]

"GuardedResponse" > wrote in message
...
> Just had a massive die off in my Malawi tank (36*18*12"). Everything
seemed
> fine about 6PM, at 12AM I had 10 dead fish - 6 yellow labs and 4 crabros.
> Tested the water and it looks like my filters crashed for some reason,
> nitrite was at 15ppm.

No possibility that you did a water change without dechlorinating properly.
Sounds to me like something just killed off you bacteria, probably about a
week prior to them dying by the level of nitrites indicated.