According to some very respected sources, anomones can up take nutrients directlyy from the water column. Specifically nitrates. I have also heard they can up take amonia directly. That does not mean they will tolerate measurable amounts with hobbiest test kits of ammonia. I know Anthony Gallo used to recommend dosing nitrates to people propagating anemones. I think the need for nitrate may be one of the reasons they do so poorly in new tanks.