Doser For Vinegar

[Madreefer]

Hey what are you people using as a doser for vinegar? I've been adding manually but my job requires me to be away for a couple days at a time plus i'm tired of doing it that way as well. I used to just put it in my FW reservoir but it created mold in there. Just started adding it to my display again about a month ago and looking for the lazy way now.