some questions about root tabs

[bobc4d]

I have a couple of questions about root tabs:

- how long do they last/how often to put new in?
- currently I have gravel substrate, I want to change to sand in the next couple of months. How long after adding the root tabs should I wait to make the switch?
- should I keep adding liquid ferts? is there a waiting period after adding the root tabs before starting adding liquid ferts?


thanks,
bob