Help - Fish Dying Rapidly

[zha50]

Hi, I'm in abit of a pinch here right now. Having not had any additions to my tank(~1.5x0.6x0.3m = ~300L), which had about 30 tetras total, for over 6 months. I recently put another 30 in, and thats when chaos struct. I had a few new Rummy's die over night so i thought it was just super weak, but then i had fish dying rapidly, almost one a day, both new and old.

Doing water tests, my Ph is 6.4(in the process of raising it to 7 with white rocks and small WC's), NH4 ~0.05ppm, Nitrite reads 0, Nitrate reads ~15ppm.
EDIT: Looks like another emperor tetra is on the way out =(, white cloudly bubble over eyes and reddish gills). Everythings going downhill...
EDIT 2 - It seems my calculations were wrong, the tank is 1.5x0.3x0.6m, which works out to be about 300L, not 150.

I noticed on the last fish that died, there was a spot about 5mm in diameter, was void of any colour, possible that the new fish came with a disease?

 

[Davo86]

150L equates to around 40G or more importantly around 40 inches worth of fish, obviously 60s tetras was overstocked.
you should have no NH4 reading, this is ammonia which even in small quantities is toxic to fish,
cloudy eyes and red gills sounds bacterial but could very easily be cause by bad water

 

[WILDER]

Reddish gills can be due to bad water quality to flukes.
The no4 reading is that ammonia reading.

Signs of gills flukes are.
Red inflamed gills or pale with excess mucas on them.
Flicking and rubbing against objects in the tank.
Laboured breathing or gasping at the top of the tank.
Swimming in a jerky movement.
Spitting food out.
Weight loss.

The spots can you describe it in more detail colour and texture.
Did the spot have any red tinging to it like a circle of red on the outside of the spot or a red centre.

Was the eye bulging out as it could be popeye.

 

[Colin_T]

tetras quite often come in with bacterial infections. If you didn't quarantine the new fish for a couple of weeks you probably introduced the infection into your tank. Try a broad spectrum antibacterial/antifungal treatment. "Wardleys Promethysol" or "Waterlife Protozin" might work.

To work out the volume of water in the tank
measure Length x Width x Height in cm
divide by 1000
equals volume in litres

When measuring the height, measure from the top of the gravel to the top of the water level. If you have big rocks or driftwood in the tank, remove them before measuring the height.

Remove carbon from the filter before treating otherwise it will absorb the medication out of the water.