all hail carbon!! why?

[Delphinus]

I wouldn't say I notice yellowing without carbon, but I do notice an improvement in water quality if I put in new carbon. I'm not sure how long the effect lasts though. It's not really that long, maybe a couple of days tops.

However I would say that it's probably useless to just have carbon passively - you need to drive flow through it. Ie., even having it in a baffle isn't probably good enough because water will just flow around it instead of through it. It has to be in a filter, either a phosban reactor or an aquaclear or a cannister filter.