How often would I need to do water changes?

Hi everyone. I have a cycled 55 gallon tank with about 700 gph filtration. I really want 2 giant fancy goldfish. I can do water changes every week, but I go out of town every now and then and I really need a tank that only needs a water change every other week. I wanted to know hypothetically if I get 2 goldfish how often would I need to do water changes on a 55 gallon.
If I cannot get the water changes down to 2 weeks, I could put the filters in a 100 gallon stock tank in my basement, if I were to do this how often would I need to change the water then?

 

that is super powerful filtration, so I wouldn't worry that much. you could do live plants, I dont know if goldfish eat stem plants or not, but you could try that.

 

I agree. With a few live plants water changes once every two weeks won’t be an issue

 

There are different varieties of fancy goldfish and some stay smaller than others. You might consider some of the smaller ones?

You might also consider fasting (not feeding) if you're only going to be gone for a weekend. It would reduce how much waste they produce.

 

What is the nitrate levels at after 1 week?