I had it ran for about a day with no change. So it would take weeks for it to make it come up? I don't have an ATO as the evaporation is very minimal. Were you running kalk at the same time as running the skimmer tube to the outside? If so, which method do you think contributed most to the risen PH? Thanks in advance for your insights.
I was running kalk in my ato long before I ran a line to the skimmer outside. It was definitely the airline outside that made the increase in my pH. I would have to been up to a dkh of 11 or 12 to get that ph before. I have a way oversized skimmer for that size tank as well though (reef octopus 110).
How much or little effect running the line outside has, is entirely dependant on how high your indoor CO2 levels are....you may have very little effect...but it wasn't an overnight change. It slowly came up over a couple of weeks.