Confessions of a goldfish serial killer.

Dear all,

by the looks of things this group is inundated with first-timers like me who
jump in looking for the answer to a question then jump out, so apologies to
any of the regulars here for my bluntness. Anyway, I have two pressing
questions that I think people here might be able to help, but first I'll
fill you in on the history of my fishkeeping disasters.

1. My friend buys me 2 goldfish as a joke, I buy a cheap acrylic tank with
ultra basic filter to put them in and buy a Black Moor to go with them, so
they're in the tank straightaway.

2. I start learning all the basics of keeping fish healthy, start changing
the water weekly and adding bacteria to the tank.

3. Unfortunately I have been changing the water from the top of the tank
using a ladle, I've been overfeeding the fish, and genuinely had no idea. I
find the two goldfish floating upside down dead and when I test the water
the nitrate and nitrite levels are through the ROOF. This leaves me with a
Black Moor who at this stage probably has a liver like an alcoholic's, so I
decant him and clean out the tank.

4. I drop the tank - it cracks. I need to get a new one quicksmart so decide
to splash out on an expensive glass one with carbon, foam and bio ball
filters. I add supplement and I buy a decent plant to convert the nitrites.
I toss the Moor in there and decide to buy him 3 new friends, fantails this
time.

5. Everything's hunkdory for about 4 weeks, then one day one of the fantails
is covered in blood bruises, as if he's been crushed. This is unlikely as
the filter isn't too aggressive, but I start to notice that there are white
spots on the other two fantails and fungal stuff too.

6. The black moor's fins start to rot away, and he spends most of the time
hiding in the little barrel I've got, out of sight, along with the bruised
fantail.

7. The moor dies (3 days ago), and the fantail is alive but hiding
constantly in that barrel, still bruised. The other two fantails are now
floating at the top of the tank constantly, covered in spots and with their
fins rotting a bit at the end too. I've tried to get them to eat lettuce and
peas - as i thought it might be a swimbladder problem - but they aren't too
receptive at all.


Now, the two main questions a

1) What did I do wrong?

As far as I can see my problem with the original tank was not cleaning it
properly (I have a gravel pump now), not allowing the nitrogen cycle to
begin BEFORE introducing the fish, and of course overfeeding.

Now I was SURE I was on the right track with this aquarium, but evidently my
big schoolboy error was to introduce the fish immediately (4 at once)
without allowing the tank to mature properly. The water quality is perfect,
though - no nitrites and very small nitrate level, so I really can't see how
they got this disease and how it's been passed on. Maybe some of you can
help answer this.

2) With 3 fish basically floating about, still alive but clearly not well -
should I consider euthanasia? The finrot treatment isn't working at all by
the looks of things and I'd hate to think that they were suffering because
of my stupidity.

Anyway, that's my confession over - obviously I'm quite annoyed about this,
I had no idea keeping fish was such an involving task but it's equally
frustrating that I'm not doing it right, so I intend to make sure that I
learn from the mistakes here and make sure that the next three or four fish
are treated like royalty.

Help!

Roberto