Not sure if my friends tank is OK

[sunflower]

OK, so I've just been to stay with my friend for a week and she has a coldwater hex tank with 3 different goldfish in there.

In the tank is a filter and a tube which contains an air stone.

Please excuse me if these are silly questions but what I'm wondering if do the "normal" rules I've come to know and love in the tropical world still apply to cold water?

Should they be adding water conditioner when they do water changes?
How often should they do water changes?
Where can I find pictures of different types of goldfish in order to identify what she has and how big they get/how much space they need etc?

Thanks in advance!

 

[black angel]

http/www.liveaquaria.com/product/scateg.cfm?pCatId=835

http/tm.ask.co.uk/r?t=c&s=a&id=30787&sv=...uarists.org.uk/

you could try here for the different types.
goldfish i personally think are more difficult to keep than tropicals. hex tanks arent good for goldies as they dont give the oxygen exchange rate they need as well as the normal rectangular tanks.
the filter needs to turn the water over 10 times per hour.
fancy body types need at least 10 u.s gallons or 8 u.k gallons each and maybe more as they grow.
you still need to dechlorinate the water and the fancy types need the water to be quite warm, ive kept mine at around 24c which is technically tropical but i find they do better at this temp.
depending on the size of tank then water changes will vary but i think for three fish in what i think may be a 12 gallon? then every couple of days around 30-40% as gf are very messy fish.
your friend should also get test kits for ammonia,nitrite,nitrate and ph as water quality quickly degrades with gf.
hope some of that helps Sunflower

 

[sunflower]

Thanks for those links black angel I'll check them out. I'm going back to my friends house in a few weeks so I'll see if I can educate myself before then