how often to change reservoir water?

Hi,

I plan on using a top feed system with 4-6 plants in a 3' by 3' area. I will use a 20 gallon reservoir.

Since I already have an RO system for the home, I will be using RO water.

How often should the reservoir water be changed?

Thanks

you should change it about every two weeks, orwhen you fuck up the nutes or ph.

Got a 27 gal w/6 plants I change every 2 weeks, I think it can go longer if I just add nutes at 2 weeks instead though, gonna start trying to change 1/month (first 3 weeks then 1 month) because it's a bitch changing it. Need to get a water pump just to empty it or something, lol.

I change my water every week. Probably more than required, but it certainly doesn't do any harm.