Zapins, I don't have any basement or any place cooler as I am living in an apartment.
Melauriga, of course, the ferns are not planted in the substrate. They are all tied to driftwoods.
Brenmuk, yes, I agree with you about nutrient deficiency leading to green spot algae. I am currently dosing Seachem Phosphorus to fight against it based on suggestion from friends.
Diana, yes, I suppose my friend's ferns are getting about 12 hours of light. I can confirm with her. Starting today, I have increased the lighting to 12 hours per day in my tank. The fertilisers used are Seachem Nitrogen, Seachem Flourish, Seachem Phosphorus, Seachem Potassium and ocassionally Seachem Excel. No iron is used currently but in the old tank (before it was broken and replaced last Saturday) had some ADA iron added in the substrate. The iron was added mainly for the Crypts (it didn't help much anyway).
In my NPT, I have some Philippines Ferns and Narrow Leaf Ferns. They look stunted as no new leaf has ever been produced. Eventually, they will consist of rhizomes only (just like my medium tech tank). Instead of green spot algae, they're attacked by BBA. No fertiliser, no CO2, no fan/chiller & no filter in this tank at all. Blyxa japonica is growing extremely well in this tank (BBA has never attacked them)- even my medium tech tanks cannot beat this tank in terms of keeping Blyxa healthy. I have not increased the lighting to 12 hours because beard algae is attacking plants such as Bacopa, Rotala, etc.