My 2.5g tank is kept at 1.08 salinity. I put a small piece of subwassertang maybe 2 months ago. There was some very slow decay (as can be seen in the picture on this wider parts). After a month it has shown tiny nodes of growth. Very tiny nodes. I just noticed it today because it is floating right now and it has more new growth that looks promising. I only put a small piece in case it decays. I didn't want to pollute my tank. But if I can get subwassertang happy growing in brackish water, that would be so cool. I will just patiently watch my experiment.