With a SOG fitted you don't need any additives and everything breaks up naturally with the air flow I do use an occasional washing tab to keep the casset clean never get smells (I know there are those that hate Sogs and park as far away from them as they can) I do change the filter regularly so I'll keep my head downWe've tried lots of different products and in our old van we even had a SOG but I've now settled on thetford blue sachets they might be slightly dearer (we pay £6.99 from camping international) but they break everything down and there's never a smell, we also use lotus toilet rolls from france as they're designed for Foss tanks so the sheets just break up completely