black spot? or worse? please help

[Kondoe]

Need help guys. i have lost 2 fish in 3 days. 1st was a tiger barb, his body was stuck onto the filter intake gaurd. i assumed he got stuck there and thats what caused his death, as i couldn't see any kind of symptoms for any sort of disease. but today i lost a golden molly, and this one was dead at the bottom of the tank, he didnt float up and on 1 side his gill had a dark grey/black patch on it. i have checked my ammonia levels and it reads 0 on 2 seperate tests. my nitrite is also 0, and my nitrate was 25 but i done a water change yesterday and at that time all fish where fine. but today i came home and found him dead at the bottom of the tank with a black make on his gill. i have looked at my otherfish and im worried if they have the same thing starting as some of them look darker almost grey around the gills (mollies) and the tigers barbs some have a very small but vivid black spot on the gill. has any1 got any idea what this is and how can i save them.

BTW, there was a power cut here in my home that lasted about 2 and a half hours, could this be a cause?

 

[allaboutfish]

do you have a liquid tester or test strips? test strips are worthless

 

[Kondoe]

do you have a liquid tester or test strips? test strips are worthless

i use a liquid test, with the drops. i also have a seachems ammonia alert disc. both show 0 ammonia

 

[allaboutfish]

here's some info on black spot http://www.fishdeals.com/fish_diseases/black_spot/ can you post a pic of it?

 

[HUKIT]

Try to post some pictures if possible Black Spot rarely causes death.

 

[Kondoe]

ok i have taken some pictures, they are not all that clear but i have marked out where i think there is a problem...

i also have a couple of videos maybe it is easier to judge the problem. here is the link:
172.mp4 video by Kondoe - Photobucket

173.mp4 video by Kondoe - Photobucket

 

[HUKIT]

How long has the tank been cycled? The areas your showing are around the gills which is normally caused by ammonia burns which are trying to heal.

Black Spots appears as cysts so with those pictures it's not clear enough.

 

[Kondoe]

How long has the tank been cycled? The areas your showing are around the gills which is normally caused by ammonia burns which are trying to heal.

Black Spots appears as cysts so with those pictures it's not clear enough.

the tank has been cycled ammonia 0 nitrite 0 nitrate 15.

it has been cycled for about a month now.
i started cycling about 3 months ago, and took 1.5 - 2 months to cycle.

 

[Gillie]

I agree that is definitely not blackspot, blackspot doesn't just effect the gill area. It does look like possible ammonia burn.