That's a very nice aquascape, good work on that.
It's rather difficult for me to ID the plants from that photo, but never mind, I get the general idea. I would get some surface plants...you mention Frogbit which is a floating plant, but I can't see it in the photo. Check our plant profiles, second tab from the left in the blue bar at the top of the page, we have several floating plants with photos.
One thing you will need is a comprehensive liquid fertilizer. Some plant nutrients are taken up from the water via the leaves, and others via the roots. The Eco-complete will put nothing in the water column, so this is essential. I would suggest Seachem's Flourish Comprehensive Supplement for the Planted Aquarium
. You use very little; for a 60g tank, 1 teaspoon once a week will likely be sufficient, dosed on the day following the water change. Another near-identical product is Brightwell Aquatics' FlorinMulti
. All of the other products seen in stores are less useful because they are not complete (comprehensive), so while they are less expensive, you are not getting what you need.
So, to your initial question on light duration. I would say 8 to 10 hours should be OK. Using a timer is a good idea to have this consistent. The light period can be anytime when you are normally home to view the aquarium, just so long as the tank receives about 8 hours of complete darkness--no daylight through windows, no room lights--every 24-hour period.
The duration can be increased slowly if you want, and as long as algae is not increasing. If algae does begin to increase (and thinking here of the "problem" algae like brush) reducing the duration may be necessary. You need to experiment a bit, but 8-10 should work.