Cory melini deaths

[Stuey]

Hi there Everyone,

I was wondering if you could offer some advice on a problem I am having with a group of corydorus melini. I had a group of 8 (3 female, 5 males) but have lost 2 males and 1 female over the last 10 days.

Temp 26 degree C
Ammonia 0
Nitrite 0.1 mg/l
PH 6.5

Substrate is rounded sand with small amounts of API laterite in bottom layer. The sand is only 1.5 cm deep and I make sure there is no gas build up within the sand.

The tank is well filtered by 2x Eheim external canister filters. The cories that have died became very pale and seemed to have laboured breathing.

There was a nitrite spike a couple of weeks ago but the nitrite is now back to as listed above. The remaining corries seem perky. A mature pair of Ancistrus temnikki, spawned during the last 2 weeks and the wrigglers are now free swimming. This morning I had 2 Geophagus Jurupari were dead with no obvious physical damage.

Is it possible that the nitrite spike from afew weeks ago has caused damage to the corries blood (I know this affects the haemoglyobin of the blood).

Any suggestions would be much appreciated.

Many thanks.

Stu

[MatsP]

Measuring ANY nitrite is a bad thing - what killed your filter bacteria to cause the spike?

Nitrite certainly affects the breathing of the fish, so it would match with nitrite poisoning - not saying it can't be other things, of course.

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Mats