Assuming some moderation and not willy-nilly, I see no harm. I keep a group of mouthbrooders in my planted and see no harm when they hold the fry for 2-4 weeks before I move them out to another tank to release them. Ferts seem to matter little to them. But when I bring the females back to the CO2 enriched tank , they do struggle for a few hours. Nothing serious but they just look "down" for a while.