Liner it also has a papyrus plant in for nitrate cycleWhat kind of pond? Concrete, liner, plastic,.......
700-800 gallons waterfall filter not much algae but it’s slimyHow many gallons, kind of filter, and algae growth?
I did put in the minnows and mollies in a little early just wanted them to produce for predators coming in but I’m not sure I don’t want to spend money and have them floating by morning I heard limestone helps with hardness and it being Florida there’s a lot of it so I might try limestoneSounds like you already understand that your liner pond is lacking minerals. Concrete ponds don't have this problem.
This being a new pond, there may be other factors and perhaps it is just not cycled yet.
Not sure had 6 mollies just to produce for future predators but all have died now just mosquito fish in itsea shells can help with hardness, also don't mollies like a bit of aquarium salt added to the water ? Or is that an old thing