I have a TDS meter to monitor but I get your point. I’ve heard this before with the initial startup of the RO unit. Challenge with the new tank being a Red Sea reefer, there’s very little space for the ATO reservoir and although it comes with one, it’s very small and I was thinking of repurposing it. Given your point, maybe I’ll just port my auto fill system over from the old tank. I’m using a 5 gallon bucket that a Solenoid fills every morning to avoid the TDS creep. I could just use this to fill the ATO tank instead, but that ATO tank is gravity fed with a float valve. My old one has an ATO monitor with attached pump. So I would probably still need to try the auto water change system in that case because the Red Sea solution won’t flush the alk tubing.
Note, when I said freshwater I meant RO.
