Here's what Seachem says I know, it's the company, but they say it's an appropriate product for starting a tank. They seem to have some gaps in thier product line, so I feel like they don't attempt things they can't support (loosely like Apple vs. Microsoft). I think it's the SafeStart that Seachem is talking about on their product page.
In my little experience, the SafeStart does grow fast, particularly if you're dumping an ounce into a 2.5 gal tank every day. The guy who sold it to me also told me I just needed to get my ammonia readings "up there" to feed the bacteria. Well, I let them get there (3 6pmm readings after 3 water changes, but all NH4. 18ppm NH4. He was an idiot.), and it killed the SafeStart bacteria. It stopped growing, started changing to nasty, rotty-like dark gray, black colors, and my ammonia was so high I decided to pretty much start over, anyway. I also noticed what looked like some kind of plant growth in my filter with it (green, until it died, then it was brown.) but no phosphates or anything else in my water. The place I bought the fish is immaculate, and with the rapid growth I got and the timing, I'm suspecting the SafeStart, but I'm just suspecting, and that's me.
I've switched (by inheritance) to the Stability, and growth seems to be slower, but the elevated NH4 readings I have haven't seemed to hamper growth. (I have a tiny, easily visible filter. It shows.) I have yet to see what happens with cycling. I've pretty much got a
double-stocked tank (could use some advice), so this is really an acid test for any product, so to speak.