Some do, some don't.....most people just use them for mini-cycles rather than for full cycling as the results are rather hit & miss.
Are you asking this because you're wondering what to do when you upgrade your tank?
If so, just exchange some filter media from your old filter into the new one and run for a few days whilst doing a small fishless cycle on the new tank (until parameters are correct) then away you go![]()
Cycled filter media from an existing filter is going to do exactly what these additives claim to do.....guaranteed![]()
Do not be impatient, the last thing you want to do is set up a new tank and move fish over causing a mini cycle and end up losing fish.
If you absolutely have to then move a few over but it will not speed up the process any quicker than following a fishless cycle routine, in fact IMO doing a fishless cycle would actually be quicker as you will be able to dose the tank with higher amounts of ammonia than a few fish will produce. This will result in a better bacterial colony and then all your fish could be transferred over in one go.
The other alternative would be to just move everything over and put the old filter into the new tank whilst running the new filter for a few weeks alongside it.