Update

Light added

I've taken the foam filter out and replaced it with a fine air stone, and moved the heater to horizontal at the back. The light's on a timer with a 12hrs cycle

                                                               
Hygrometer and TDS meter, added 195gms Marine Salt
for a Specific Gravity of 1.012 (Brackish)
added 5ml API Qick start (Bacteria) to start the Nitrate cycle
added x10 drops of Ammonium Chloride to feed the Bacteria
then time to play with the API Saltwater test kit

I've upped the tank (approx 20ltr water) to 75*F
195gm Marine Salt = SG 1.012 (Brackish)
16/02/18 --------- 5ml API Quick Start
19/02/18 ---------- x10 drops Ammonium Chloride
API Ammonia test = 2 ppm
21/02/18
API ph test = 7.8
API Ammonia test = 1ppm
API Nitrite test = 0.15 ?

Because I couldn't get the Coral gravel to wash clear and added an inert substrate I added a piece of Coral to act as a PH Buffer