Topping off & Air space

[warminghut]

In much of the info I have read about making cider in books or on the net, I see instructions to keep the fermenting cider topped off. Is this necessary when using glass carboys and airlocks, or only required for casks and larger vessels? I currently have a 5 gallon carboy with 3 gallons of cider, and a gallon jug with a half gallon of racked off cider. Am I doing harm, or worrying needlessly?

Thanks for any help. I have about 11 gallons currently fermenting, another 120 lbs of apples sitting in the kitchen, and whatever I pick up at a local orchard's end of season sale. Can't wait to see how it turns out.

 

[AndrewTodd]

If your still in active primary fermentation I see no problem with that headspace. If your near the end or in secondary and are taking readings every day looking for a target FG then your introducing a lot of air on that larger surface. Secondary in as small a vessel as possible.