My Fish Died I Need Help!

[jeepgirl]

my fish that I had for 13 years just died today and I want to figure out what I did wrong. First of all I don't know if it had anything to do with this soar he has had I think it was a ulcer but I am not 100% sure of that anyway he had it for about 6 or 8 months and I tried med's but nothing helped. So I don't know if it had to do with that or something else I did wrong. My daughter told me she seen him hitting the top of the fish tank like he wanted to get out when I came in the room I seen him hit the bottom of the fish tank with his nose one time than he laid down and just quit breathing. I tested his water with one of those test strips and to my best that I can say the ph was 7.0 the alkalinity was between moderate and ideal, the hardness was between soft and hard the nitrite was at 0 and the nitrate was about 40 so I am guessing that it might of had something to do with the nitrate being that high but does anyone have any suggestions? I am confused on the ammonia the color it showed was lighter than the ideal color on the chart so that would tell me that it's not high since all the colors on the chart telling me it would be high is a light green to darker green and the ideal color is a light yellish-green and what the test showed was lighter than the ideal. I am just trying to figure out what I did wrong. One other thing and I don't know if this is from him hitting hisself or something else but after he died he had something coming out of his chin like either a long string of blood or maybe a long worm??? Any advice to what the problem could of been would be really apprciated I was thinking about using the same tank for other fish but I didn't know if I should start all over and empty all the water out and clean everything and start all over with new filters and new bio fiber and let the tank go thru the cycle or if it was ok to keep it like it is and just try to get all the levels the way it is suppose to be than add new fish.

 

[AstonN24vantage]

what kind of fish? maybe it was old age?

sorry for the loss.

 

[jeepgirl]

what kind of fish? maybe it was old age?

sorry for the loss.

It was a black ghost knife fish, it just makes me so sad it's hard to look over at his fish tank without him being in there I can't help it but I was attached to him just like any other animal I had. I guess 13 years was a good life for a fish I just hope I didn't do anything wrong.