It's a 55gal tank with three very small goldfish in it. I have two generic topfin filters (60 and 10)

How often do you think I should change the water?

That's hard to say without knowing
1. The water perams. Do you have a test kit? do you know if the tank is cycled?
2. The gph of the filters, is there any way you can find that out?

50% weekly. Replacing with temp matched, treated tap water (i use Prime).

I'm cycling it with the fish in there. I just really needed to get them out of the 10gal. Pretty much, they're very healthy and hardy, as I had the ryukin and the fantail together in a bowl for 3 months doing only one water change, and neither of them have EVER (knock on wood) had any visible health issues. The water params are;;

Ammonia: 0ppm
Nitrite: 0
Nitrate: 0
pH: 7.3

No gH or kH tests are available, but I'm guessing that my kH is pretty good seeing as the pH is completely stable.
The tank has been up for 3 weeks and has had fish in it for 1 week. I also have old filter media in the filters from the tank I just dismantelled, as well as some of the substrate and decor. Hopefully this will speed up cycling.

I would imagine, with the size/amnt of fis in there, it should be awhile before i have a noteable amount of ammonia/nitrite

Well I just put my 3 large goldies in a 50 gallon with established filters. I'm planning on doing my usual regime of 25-30% water changes every 5 or 6 days. I don't think you need to do 50% unless things really start spiking. It's more of a 'guess and check' process. If you notice ammonia climbing, start doing large changes right away. If everything seems cycled, you may be able to just do partial changes every week.

Cool!!!!

By the way Katherine, your TOP FIN 10 pumps 50 GPH and your TOP FIN 60 pumps 300 GPH. So, for a 55 gallon that is somewhat underfiltered. You need one or more filters that pump 200 GPH.

I knoww, i'm just broke right now. D: thats why i'm holding off on getting a ranchu that i want so baddd D:

Hi Katherine

I used to have one Shubunkin in a 55 gallon, and I still changed out at least 50% of the water each week. They need the fresh minerals and electrolytes from the fresh water, and it also cuts back any bacteria build up, which you can not see. It's also a good time to get in extra fish kisses!!
Just remember to keep testing, and do extra water changes if necessary.

My fish were also in a fish bowl for a week, (there were two) and then they also went into a 10 gallon. I unfortunately lost my Smokey in December, after battling Columnaris - but my Dot is now happily living with another board member in a large pond with many friends.
It's interesting that we've both gone from bowl, to 10 gallon, to a 55.

Best of luck with your new tank!! I'm sure your fish are loving their big home!!

Debbie