FW Top Off

[Fresh2o]

I recently changed my lighting in a 20g long and now it's topless. Of course, evaporation has increased. What should I top it off with? I do not have an RO system. Will distilled water be adequate? Are there any other options?

 

[Rivercats]

I use RO since I have a machine BUT if you are deligent about your weekly WC and evaporation isn't massive then you can use tap water. I used to do that before I got my RO machine.