Is there any down side to going with flourite but keeping the tank lightly
or moderately planted? Algae, perhaps, or something else I should consider?
As Leigh said, no problem at all.
I'd add that if you're only going to plant one area of the tank you
might consider saving yourself some money and only put the Flourite in
that area. Flourite is a good deal more expensive than plain gravel,
and every dollar you save can be spent on more fish