Check,
I would try to add some plants that can utilize a bicarbonate source for carbon such as Vallisneria or egeria densa. The idea is to use plants that can outcompete the algae your java ferns and banana plant grow relatively slow. Since you added fertilizer to the system I would think that you have fairly high phosphate levels, and this is the nutrient that is often limiting plant and algae growth. By changing water so often you are also adding more nutrients to your water. The best way to beat algae is usually to let the right plants in high enough numbers outcompete. Plants that grow out of the tank or on the surface,ie..water lettuce, duckweed, are also great for beating algae.