how come you've got 2 clowns in your tank, but your ammonia is 0.5 and your SG is so low? :/
I would say he probably had an inaccurate test reading or was at the end of cycling. I usually take a water sample to the lfs
every month or so to see if my measurements are correct.
1.017-1.020 in a FO
tank helps keep parasites (ich etc.) from thriving. It is a strategy used by most lfs
and commercial holding / breeding facilities. The cost of salt is less, parasites reduced, and oxygen gas exchange is increased. Fish use less energy expelling salt to keep their osmotic balance in check also. It cannot be used with corals or some inverts AFAIK