The basic of is salt is salt. Now let me explain before you roll your eyes. Some salts are made artificially which guarantees purity while others use salt from evaporation, giving you more trace elements. Salts like RSPro have lots of trace elements added so if you are ignorant of that fact you will have trouble when you dose additional unneeded elements, like a spike in alk. I started out 3 years ago using IO reg. Then with a new tank went to IO crystals. I had good results with both. After seeing several tanks that I personally saw their growth and beauty, I asked what salt they used. It was RSpro. So I tried it and liked it but I made the mistake of also dosing while doing 15-20% water changes. That led to a huge alk increase. Since I have changed to 10% water changes and always mix the salt to a salinity of 1.025 and not any higher, I have very stable and healthy tanks. I have not tried Tropic Marin.