Light with a kelvin rating under the 6500k (ie 4000 or 3500- aka soft white or cool white bulbs) will not have any effect on your plants.
I wouldn't put in floaters if you want rooted plants. You really don't have enough light that you can afford to shade anything you root in the gravel.
The rooted plants will take up nitrates, but only as quickly as they can grow. The light in this case will be the limiting factor when it comes to growth. More plants will equal more nitrate reduction.
The one nice thing about floating plants is that they will be close to the light and can take CO2 from the atmosphere so they will grow quickly and be absolute nitrate and phosphate sinks- they are going to suck that stuff out of the water so fast you won't believe it. The thing is, while they will help with water quality they're not really going to help much with decor- which I think is one of your primary desires here.
Anubias and Java fern - you can use a rubber band to attach the rhizome to a small rock (go look outside, you don't need much rock to make them sink) Swords and crypts can be planted right in the gravel. Moss sinks so you don't have to tie it down although it tends to look sloppy if you don't.
I wouldn't put in floaters if you want rooted plants. You really don't have enough light that you can afford to shade anything you root in the gravel.
The rooted plants will take up nitrates, but only as quickly as they can grow. The light in this case will be the limiting factor when it comes to growth. More plants will equal more nitrate reduction.
The one nice thing about floating plants is that they will be close to the light and can take CO2 from the atmosphere so they will grow quickly and be absolute nitrate and phosphate sinks- they are going to suck that stuff out of the water so fast you won't believe it. The thing is, while they will help with water quality they're not really going to help much with decor- which I think is one of your primary desires here.
Anubias and Java fern - you can use a rubber band to attach the rhizome to a small rock (go look outside, you don't need much rock to make them sink) Swords and crypts can be planted right in the gravel. Moss sinks so you don't have to tie it down although it tends to look sloppy if you don't.