In message , Fuzzy Orange
writes
sophie wrote:
If none has been changed for three weeks after moving house this might
be your problem; also if you added three new fish you've doubled the
bio-load on an already overstretched system (your stocking levels are
a fair bit higher than recommended) and the filter isn't coping with
the extra waste. Did you notice vaguely cloudy white water at any point?
Basically, your water has been getting slowly more toxic over the
last three weeks. You should probably do fifty percent water changes
daily (and do use something to get rid of the chlorine) for a while
and then keep a close eye on your ammonia/nitrite/nitrate levels. If
you do intend to keep all those fish in that tank (which no-one here
will recommend, btw!) you're going to have to be absolutely religious
about water changes and you will need to under- rather than over-feed.
The white spots could be Ich, I'm not sure - you'd need someone who
knows more about stuff than me to deal with that one...

Are you serious?

The tank is nearly 3 foot long and has 6 fish in it - it looks nearly
empty!!

'fraid so. (it's a _really_ common misconception, if that's any
consolation; I made exactly the same mistake. only worse!)
your tank is about 28/29 US gallons. goldfish out to have - wait for it
- 10 US gallons per fish, due in part to the amount of waste they
produce which is gigantic compared to most other fish. It's really hard
for an aquarium to have a relatively stable ecology with a high
goldfish-load. (I think plecos are pretty bad, too) The other reason for
this is that you need to bear the adult size of a healthy goldfish in
mind, which can be a foot. Six foot-long fish in a three-foot tank would
be kind of unkind...

I like the idea of space in the tank (crowds give me claustrophobia),
but on the other hand I've chosen to out three goldfish in a four foot
tank. I could fit in another one and a half (!) if I wanted to, but
instead I've got a small school of WCM minnows, which are sweet, and
have weather loaches in quarantine waiting to join them for a bit of
variety. They also make the tank look more interesting, not to mention
fuller. Goldfish purists will disagree with me, I think, but this works
_for me_.

Have you been introduced to the nitrogen cycle at any point? if not, it
would probably help your understanding.

hth,

--
sophie