I have a 20 litre tank and I do it like this.
Get home from work and fill back to the top with plain water. After a couple of hours test the ec. It can sometimes be down as low as 0.7ec. I normally aim for about 1.1ec and I know how much
nutrient to add to get to that.
1ml micro, 1ml grow, 1ml bloom takes it up by 0.1 ec.
So in the case of it being 0.7 I add 4ml of each to get it to 1.1.
I repeat every day normally.
Then every couple of days I check the ph but wait a few hours after nutrient is added to allow the buffers to stabilise. Then 0.5ml of ph up gets me from 5.8 to my desired 6.0 - Rain water by the way.
Chris