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On the basis of the tank being filtered, which from your profile I don't think it is???

Is there a particular reason you don't use a filter?

oh yes! I hadnt noticed they didnt use a filter. You will want to be doing big water changes then!

You definatly need a filter Lucy or your fish will die.

2 goldfish in a 40L tank without a filter is going to cause problems quite apart from the stress of being chased and removed each week

Have a read of this:

~KEEPING GOLDFISH - THE RIGHT WAY ARTICLE~

Goldy, this article suggests changing charcoal every month, I was told every 8 weeks, So which is correct.

I have all fancies.

it depends on brand and quality of the carbon most of them have a time limit on the box but monthly is average

It also depends on the chemical contents of the tank, if theres lots to absorb the carbon will fill up quicker

As the others have stated depends on the brand, I use Rena bio-chem zorb in my tank and this states 2-3 months

where as the API one states 3-6 months, see link below

http://www.petsparade.co.uk/aquarium/filter-media/?p=4529

Ok guys thanks for your input, I have decided that as the pkt says 8 weeks I will mark on the calendar for 6weeks.

I would rather do it that way and know I am not stretching things.

Thanks so much for all you advice - catch you on another thread!

great link, so true, if only every one would read it before buying fish!

Unfortunately I learned the hard way, but I'm glad to see that I'm now doing most things right :)