I haven't tried any new ones or heard from any reputable source that they work but I don't pay attention to them anymore so there might be something out there that works.
Why are you setting up 15 tanks in a hurry? Not trying to knock you just trying to get the whole picture to better help.
For mass fast cycling I would take an empty tank, line the bottom with air diffusers, then egg crate with media on it (seeded media at the bottom) and dose pure ammonia till all the media is cycled. With a good batch of seeded media it shouldn't take long at all. If you are using sponge filters as your main filters, take the dirty sponges and squeeze them out onto your new sponges (get your sponges dirty, yes lol) and then run those new sponges with the ammonia till cycled.
Depending what you are trying to achieve with these tanks, packing them with fast growing plants can make a huge difference. Pothos roots in the water is a big nutrient absorber too.