I currently have three divided 10g tanks, one 6.6g, one 5g, and one 20g sorority. They are all heavily planted/filtered/heated/cycled.
I know a lot of fish keepers run into this issue, but I am possibly needing to be out of town for almost 2 weeks (11 days) in October. I will do a 50-75% water change the day before I leave. I have someone to turn on and off lights accordingly, and they may be able to do a mid-week water change on the smaller tanks, but how would I handle water changes on the 10's and 20 gallon tanks? How long can they respectively go without a water change??