So I should skip the cuttlebone and try a pinch of baking soda if I only want to raise the kH ?
Here is a link to an article I've only just started reading - however this caught my eye (the italics are theirs) since I don't add co2 to may tanks...
"KH (carbonate hardness) is an important source of energy for nitrifying bacteria that eliminate ammonia and nitrite. In addition, carbonates may be used by plants for photosynthesis when carbon dioxide (CO2) is absent
and the link to the article if anyone's interested. They do push Seachem buffers rather than baking soda, but this is a sales site; http://www.americanaquariumproducts.com/aquariumkh.html