Okay, so I have no experience with the Fluval Sea 3.0 LED. However, I did pull this off of their website: [TABLE="class: tablepress tablepress-id-14 tablepress-responsive dataTable no-footer"]
[TR="class: row-1 odd"]
[/TR]
[TR="class: row-2 even"]
[TD="class: column-1"]
UPC[/TD]
[TD="class: column-2"]015561145145[/TD]
[TD="class: column-3"]015561145152[/TD]
[TD="class: column-4"]015561145169[/TD]
[TD="class: column-5"]015561145176[/TD]
[/TR]
[TR="class: row-3 odd"]
[TD="class: column-1"]
Size Range[/TD]
[TD="class: column-2"]15 - 24"
(38-61 cm)[/TD]
[TD="class: column-3"]24 - 34"
(61 - 85 cm)[/TD]
[TD="class: column-4"]36 - 48"
(91 - 122 cm)[/TD]
[TD="class: column-5"]48 - 60"
(122 - 153 cm)[/TD]
[/TR]
[TR="class: row-4 even"]
[TD="class: column-1"]
PAR / LUX (Depth)
3" (8 cm)
6" (15 cm)
12" (30 cm)
18” (46 cm)[/TD]
[TD="class: column-2"]
370/ 15 000
181 / 6600
65 / 2400
31 / 1200[/TD]
[TD="class: column-3"]
376 / 16 290
222 / 8750
90 / 3620
47 / 1940[/TD]
[TD="class: column-4"]
381 / 16 720
236 / 8910
94 / 4160
55 / 2440[/TD]
[TD="class: column-5"]
390 / 17 120
243 / 9210
102 / 4270
63 / 2580[/TD]
[/TR]
[TR="class: row-5 odd"]
[TD="class: column-1"]
LEDs[/TD]
[TD="class: column-2"]99[/TD]
[TD="class: column-3"]168[/TD]
[TD="class: column-4"]252[/TD]
[TD="class: column-5"]336[/TD]
[/TR]
[TR="class: row-6 even"]
[TD="class: column-1"]
Wattage[/TD]
[TD="class: column-2"]22 W[/TD]
[TD="class: column-3"]32 W[/TD]
[TD="class: column-4"]46 W[/TD]
[TD="class: column-5"]59 W[/TD]
[/TR]
[TR="class: row-7 odd"]
[TD="class: column-1"]
Lumens[/TD]
[TD="class: column-2"]850 lm[/TD]
[TD="class: column-3"]1350 lm[/TD]
[TD="class: column-4"]1950 lm[/TD]
[TD="class: column-5"]2550 lm[/TD]
[/TR]
[TR="class: row-8 even"]
[TD="class: column-1"]
Color Temp.[/TD]
[TD="class: column-2"]25 000 K[/TD]
[TD="class: column-3"]25 000 K[/TD]
[TD="class: column-4"]25 000 K[/TD]
[TD="class: column-5"]25 000 K[/TD]
[/TR]
[TR="class: row-9 odd"]
[TD="class: column-1"]
Lifetime[/TD]
[TD="class: column-2"]50 000 hrs[/TD]
[TD="class: column-3"]50 000 hrs[/TD]
[TD="class: column-4"]50 000 hrs[/TD]
[TD="class: column-5"]50 000 hrs[/TD]
[/TR]
[/TABLE]
I'm mainly looking at the par levels. Sticking with mainly lower light corals, depending on the depth of your tank, you should be fine. Towards the bottom (if your tank is 18" deep), then you are a little low on PAR (for me - I usually try to run about 150 PAR or so on the bottom). The upper level and middle you should be fine.
That said, I would do the 48" but that's because I don't like shadowing on the sides, however the PAR difference isn't going to be huge.