I did some impulse buying tonight. I purchased 2 very small puffers. The are a 1/2" long. The tank was labeled "Freshwater Puffers". I think I screwed up. I am placing them in my 30 gallon tank and my nephews are taking the guppies. Should I add salt to this tank to make it brackish? If so how much? I have some instant ocean on hand and can add salt if needed. What's the salinity I should shoot for however? I'm also posting this in the brackish forum...