, for fish only, instant ocean works fine. You don't really need to worry about the levels of calcium, strontium, etc. That's why most people with extensive reefs use more expensive salts. Algae's grow because of lighting and excess nutrient issues so unless you are buying a salt that has lots of phosphorus in it or comes laden with fish waste.. I'm doubting that the salt is going to contribute to an algae issue. However, I'm sure the pet store employee would prefer that you buy a more expensive salt from his store. If instant ocean has worked for you for 10 years... I'd say it works for you. If you plan on someday switching to keeping coral, at that point I would probably look into the change.