Macro nutrients they are solid tabs of organic slow release nutes that break down slowly and should last the length of a grow. I wanted to use two at the start adding a third around the third week. Ended up 1 at the start and two more now. If your using 10-15 litre pots you can use two tabs. I add bacteria and myco (bactrex, mycotrex )to create a living soil that helps make nutrients available and healthy plants naturally ". I also amend the soil with Sillicium flash to provide micro nutrients And I use bio PK 5-8 during flower . I know you only asked about the tabs but thought I would run down my nute regime, all Organic and allows me to control nutrition as I am not always around. Mostly people just add water.check out the Bio Tabs section on AFN