another dead fish

[Jonah]

After quite a few good days with no deaths, following the 25%water change, I have come home to find another dead red eye tetra. His eyes were gone also.

I had been to the pet shop in my lunchbreak to look for a water testing kit, hoping to get the whole shebang but they only had a nitrate testing kit so I bought that (better than nothing) TEsted the water and nitrates are25mg/l. Not bad for most fish according to the chart, but would benefit from a small water change. All the other fish look healthy and seem well. Hubby suggests perhpas fish supplier not all that good as they often have dead fish etc in the tanks being eaten but they are a proper fish supplier with marine tanks also, not your local pet shop type set up.

What is wrong? Any suggestions gratefully received please asap to avoid further deaths.
tank is 56 plus litres
no plants
1 piece of bogwood which I have had for ages
I have had the gravel for ages, tank is mature and was subject to fishless cycling when new anyway. I have read lots of links but cannot seem to pinpoint the answer. Any help please.

 

[Avalon66]

what size tamk is it?... I had bought a 10 gallon tank and it came with a filter only to find out the filter was not large enough to do the job.. I went through 10 fish before finding out it was a matter of adding another filter... Now i have two filters in the tank.. the one that was given with the 10 gallon that was suppost to be for a ten gallon tank and a five gallon filter.. I have not lost a fish since.... personaly i think the filter i got with the tank was only a five gallon filter .... if you have a friend that have fish ,,, see if they have a extra filter and trying adding it to the tank and see how it goes.... i noticed the difference in the water quality within the hour....of adding it... good luck dude .. i know how you feel it sucks when your fish die....

 

[Jonah]

Thanks for your reply, however this tank has been running for a long time now and the filter has always been ok so far. I squeeze out the filter gently in old tank water from time to time to clean it out a bit and the nitrate test results weren't too bad although I intend to do a partial water change tomorrow. Does anyone know why his eyes were missing as I have never had this happen before. Also does anyone find that fish from some places don't last as long as ones from other places, as I had some fish a while ago from a different supplier and I have still got those and they are all ok! Strange isn't it.

 

[Avalon66]

I had a fish loose an eye because of the filter.. he got to close to it and it pulled him in... by the time he got away from the filter it had pulled the eye out of the socket.... I found gold fish tend to have that happen to them alot .... Thats just one of the reasons why i like platties..... they are more hardy...