Afk Fish farm

I have built an afk fish farm, then i read some threads (not all of them) and i have some questions about when or when not im allowed to use it. I do not want aternos servers to lag or have some issues with this. First of all - Am i allowed to use it if im afk fish farming but my friends are doing something on the server? second question- If there are no players online but me, how long would it be ok for me to use it for? How frequently am i allowed to use it? (like, once in an hour or?)