I personally feel like Petco water isn't worth it. Synthetic salts have grown massive coral colonies and kept wild and domestic fish/coral healthy for decades.
Not to mention, at far less than $1 a gallon for saltwater (depending on if you buy it from an LFS or mix it yourself), it's FAR cheaper too.
I suppose if you don't have any corals, have a tank less than 5 gallons in size, and don't mind paying extra cash for something you can get cheaper, then it's decent.
But far beyond that point, it's Petco, and i'd rather not ever give them my money. Cruelty to animals is not my thing.
I used to use IO Reef Crystals with great results (still do in the 5g pico) but in the 40g I now use Seachem Salinity (since it's free for me) and still have fantastic results. Look up the chemical makeup of their salt vs. others. It's impressive.
If you have to buy expensive natural water, then add all these supplements just to keep coral alive and healthy, is it worth it? Not to mention, you never know the chance of bad stuff that could be in that water.
0 TDS RO/DI and an exact salinity mixed by myself gives me the piece of mind I prefer.
I know everything I just said, was already said, lol. So IDKY I really even resaid it. Guess to just throw my own experience in.
That being said, owning a 5g pico that barely needs any water for the WC, maybe I will try a box of this just once and see if I too notice a change in anything. If I can get it for under $18 that is... Lol.
What's the salinity inside the box?