Since i last set up my marine tank ive forgotten what the equation is to work out how much salt you need to put in per gallon.

Ive just got a Boyu Orca setup which is a 58ltr tank (12.73 uk Gal) And need to salt it.

About half cup per gallon if my memory serves me correctly, and then fine tune to what salinity you want.

kool, ive worked it out to be 1.8kg for 12 gallons, so will add it slowely and keep an eye on the hydrometre

That's the way mate, long time since I kept marines. I think there is a difference in salt density to what you intend keeping, like fish only opposed to a reef. There will be some salty's on later, they will advise you.

ive got an 8 x 4 x 2 marine setup already with a breeding pair of porcupine puffers and a couple of pterois volitans (lion fish) in. just setting up one in my bedroom for a few clowns and forgot what the measurements were! lol

you got any photos love to seen that mate sounda agreat

You need a salinity measuring instrument (hygrometer?) looking for 1.024 to 1.025 salinity.

I believe salt is calibrated to be mixed at 75oF. So, you need your water to be at this temp to give a true reading. Not to sure on salinity, 1.024????

Do you not do water changes on your big tank.