Naja, would you recommend switching from Carbon pads to Seachem Purigen
paks? my thinking is the carbon is removing ferts the plants could be using,
so the plants are not as efficient as they could be at supporting the bioload,
also carbon is not doing as good a job removing Nitrites as Purigen would do,
at least until the biofilter media inhabitants do a better job keeping up with it.
mcd, despite your obvious precautions, it still sounds like you are overfeeding.
unless you have fish/shrimp fry, feeding even less, once a day, should be fine.
don't be too concerned with crude under your gravel, that's good crude
it's the stuff you seem to accumulate on top or your gravel that's an issue.