4 Dead Fish

[zoeb2912]

Just got back from fireworks display with the kids and noticed 4 of my fish are dead! both otos, 1 danio 1 cory
 
They were fine yesterday......
 
would normally do a large water change but got a feeling its the nitrates and dont want to add to the problem, will be buying some nitrate minus and nitrazorb tomorrow
 
 
 
Tank size: 24 x 12 x 12 15g 57l
pH: 7.6
ammonia: 0
nitrite: 0
nitrate: 40-80+ always a problem as comes out of tap 80+
kH: ?
gH: ?
tank temp: 24

Fish Symptoms (include full description including lesion, color, location, fish behavior):
 
no symptoms

Volume and Frequency of water changes: 50% weekly

Chemical Additives or Media in your tank: easycarbo, easylife ferro, and another easylife fert, cant think of the name

Tank inhabitants: was 30 danio erythromicron 2 otos 1 bnp 8 pygmy cories 10 lampeyes

Recent additions to your tank (living or decoration): 8 pygmy cories 2 otos

Exposure to chemicals: none

Digital photo (include if possible):
 

 

[nic1]

Hi.
You are over stocked. With a bio load like that you would need to be doing 70-80% water changes every week or 40% changes twice a week.

 

[zoeb2912]

Done an 80% water change today and added nitra zorb to my external filter. Also added Tetra nitrate minus. Hope they work. will do water tests every day for next week to see how things go.
 
I thought I had lost 2 otos but one is still swimming about so it must of been my bnp as it was too large to be any of the others, shame, was a gorgeous looking fish.
 
I def found 1 dead oto, 2 cories and 1 danio and what i think was my bnp. 
 
Added a pic of tank after adding the nitrate minus, very cloudy, 
 

 

[Byron]

Without suggesting this is the direct cause, I do agree that there are too many fish in this tank.  The tank is a bit small for the the Lampeye (presumably this is the African killifish species Aplocheilichthys kingii) alone, and regardless of tank size I would not recommend this species be combined with the Danio erythromicron.  I had a group of the latter numbering ten in a 20g on their own, so 30 in a tank with less volume is pushing it.
 
I agree you need to do something to lower the nitrates.  Nitrate should not be above 20 ppm max, and preferably no higher than 10 ppm.  Are you certain they are 80 ppm or higher in the tap water?  In the US I believe 50 ppm is the highest allowed, and this can be dangerous for humans (children, mothers expecting, etc).  I'm not suggesting nitrates killed these fish so suddenly, but this is an issue that needs fixing, as the high nitrates do weaken fish over time so this could be a factor.
 
Byron.
 
Edit.  See you just posted.  I would not replace the BN pleco.  Just occurred to me concerning the corys, is the substrate sand?  Pygmy corys do not fare well with anything but soft sand.

 

[zoeb2912]

Without suggesting this is the direct cause, I do agree that there are too many fish in this tank.  The tank is a bit small for the the Lampeye (presumably this is the African killifish species Aplocheilichthys kingii) alone, and regardless of tank size I would not recommend this species be combined with the Danio erythromicron.  I had a group of the latter numbering ten in a 20g on their own, so 30 in a tank with less volume is pushing it.
 
I agree you need to do something to lower the nitrates.  Nitrate should not be above 20 ppm max, and preferably no higher than 10 ppm.  Are you certain they are 80 ppm or higher in the tap water?  In the US I believe 50 ppm is the highest allowed, and this can be dangerous for humans (children, mothers expecting, etc).  I'm not suggesting nitrates killed these fish so suddenly, but this is an issue that needs fixing, as the high nitrates do weaken fish over time so this could be a factor.
 
Byron.
 
Edit.  See you just posted.  I would not replace the BN pleco.  Just occurred to me concerning the corys, is the substrate sand?  Pygmy corys do not fare well with anything but soft sand.

 
No the lampeyes are Micropanchax macrophthalmus, no bigger then an inch fully grown. They are upper water peaceful shoaling fish so are fine with the danio which reside in the bottom half of the tank.
 
I doubt there are 30 danio left, i would guess at 20 but impossible to count without catching, I found 1 dead so there was probably more I havent seen, tank is heavily planted.
 
I have checked my tap water numerous times and its always 80+, thats straight from the tap and after letting it sit for 24 hrs.
 
I will not be replacing the bnp.
 
And yes I have sand substrate
 
Thanks
 
ETA the substrate is aqua one silica sand 1-3mm