None at all, the soil mix was 1-1-1 , the perlite drains and leaves air pockets, the vermiculite helps absorb the moisture from the wicks. Once the plants are in flower they start sucking up a lot of water. Toward the end I would fill up the trays every day. In the beginning , maybe once a week.
Oh... the buckets were on bricks in the trays, so the bottoms weren't soaking in water. The wicks came out of holes in the buckets and down into the tray of nutrient solution.
It was more effective than top feeding and less mess.
I grow in waterfarms, ebb and flow tray and hempy buckets now. But for an easy to use system that you can make from readily available materials, it can't be beat.