Hi Neji:
I don't know how if you get "bored" with
FW you could handle a
SW tank. A SW set-up is a whole different ball game. FW experience is handy but marine tanks are not as tolerant as most FW.
The only things you could keep and use in SW is, in my honest opinion, your current light settings and the tank itself, if and only if, you are going to keep a fish only with
live rock tank (
FOWLR). In that particular set-up, the lighting is only important for you to see your display.
Forget about gravel. Aim at 20lbs of aragonite sand or alike. And of course at least 15 lbs of live rock. That shall live your water volume around 6 gallons unless you use a
sump/
refugium.
SW is quite unforgiving when overstocking is done. Water parameters can be a real challenge to keep within a stable/healthy range in such a small tank.
RO or even
RO/DI water should be considered as the only source of water.
Some essential testing is needed, from
salinity (measured in two ways:
specific gravity or parts per thousand);
pH, as well as
ammonia, nitrites and nitrates. You probably won't need to measure Ca, Mg, or PO4 if you stay with FOWLR.
I invite you to read around marine species for beginners that are suitable to Nano SW FOWLR set-ups. Good filtration is obtained mainly from biological filtration through live substrate (sand and rocks).
By the way, I'm a newby in SW.
Pepetj
Santo Domingo