I have tried Io then Io reef crystals then ESV and now am looking to switch to H2ocean for the 125g. I never had a prob with either of the IO salts but then again at the time i wasnt worried about cal/mag/alk. Just Ph, SG, temp hehe.
When i moved to ESV it was perfect everytime i mixed it. Dissolved well and quickly and levels wer right on. But for me..... i would only go back to ESV if i were mixing large batches of water and not have to mix for atleast a month.
That was not my situation now where im in a small apartment and have to make ro/di water then mix it and perform water change all on the same night and repeat every week.
If you like to do 2 smaller water changes weekly which i used to do but stopped because of the esv mixing..... its even worse. Some guys like doing this. And i would deal with it if need be..... but i hear alot of great things about H2ocean. So even if its 2nd best to esv.... im happy with 2nd best and less mixing.
How many gallons are you changing out? I just bring a bucket to my LFS and they fill it for $1.50 a gallon. I only have a 14 gal BC so this works for me and they use sea Chem salinity.