IO is my choice, and yes I've tried others. Really could tell no difference. There are too many variables already, and chasing numbers in search of reef nirvana is a fine pursuit for some. I like the consistency of state-of-the-art manufacturing over some boutique brand that may or may not be here one day. Here's some info I ran across:
"Very recently, the company moved its manufacturing facilities to Blacksburg, Virginia, where its parent company, United Pet Group, has its principle chemical manufacturing center. The over 200,000 square foot facility features all new, stainless steel, pharmaceutical-grade equipment. Also, the company has a state-of-the-art, temperature-controlled laboratory dedicated solely to testing salt. This is where quality control is maintained through regular sampling and analysis. In making this manufacturing move, the company’s goal, given its long history, was to maintain and strengthen its trusted brand name in the market. Its mission remains to provide a consistent and reliable product to customers.
Over the years, and leading up to the move, modifications have been made in order to remain at the forefront of manufacturing innovation. Perhaps the most significant investment was in upgrading to computer-controlled processes. Every ingredient is now weighed on a digital scale and added by computer-controlled valves to ensure that each batch of Instant Ocean is exactly the same mix. The updates have also improved overall flexibility in manufacturing to efficiently meet customers’ orders, without compromising on quality."