All my fish died

[Vics128]

Any ideas? they were cold water fancies, they where fed once a day, 1/4 tank clean every month, had a filter, and had all the additives that should of been added.
We got 6 in January, lost one a month later, and the rest have followed suite aprox 3 weeks apart till today when the last one died. The snail that appeared is sill ok. I would like to get some more, but obviously dont want to be responsible for 6 more deaths. They didnt have any signs of illness. Thanks in advance

[wildwood]

Is the tank in full sunlight for a lenghth of time during the day?

[True Blue 36]

are you over feeding them? the extra food that is not eaten could be poisoning the water. Buy some water test strips to makes sure it is all ok. Make sure nothing can get in the tank and make sure you hands are clean when you feed them.

[B00]

Hiya, im assuming it was a new tank with new fish introduced? If so, it sounds like New Tank Syndrome.

http://www.fishtanksandponds.info/care-mainten ance/health/newtanksyn.htm

[B00]

PS
Also, just to clarify, even though the link refers to tropical tanks, the same also applies to coldwater ones.

[Kiwibird]

Cold water fish need only be fed every 3 - 4 days. In fact over feeding can cause them to die and also can poison the water. Over crowding can be another issue.
You don't say how big the tank is or how many fish, but a general rule is for every half inch of fish, there needs to be 2 litres of water.