how often do i water with rock wool and clay balls?

i assume you mean and ebb and flow or flood table type grow by the water cycle... that is a pretty heavy feeding schedule.. you only really need to feed 4 times a day for 15 minutes at a time... that would more than suffice.... but as long as your plants arent looking over watered they are fine..

i thought that it was too often. they are doing great with the currunt water. what are the first signs of over watering that i should look out for? and is it beneficial to increase the amount of light from 20 hours to 22-24 hours?

If your plants start to droop, or the leaves turn over. Then it's too much

i flood three times a day for 15 minutes to start then later on move up to 30 minutes. but when i started i was only using 5 inch net pots with hydroton and rockwool so i had to flood 6 maybe 7 times a day. the more hydroton the less often you gotta water

it is now day 14 since the start of my clones. with a 20-4 light routine and flooding for 15 minutes every 2 hours all is well. this is my first grow and i am only growing 2 clones in a closet. there is a new leaf at the top of each plant every 1.5 to 2 days. one clone is 13cm tall and the other is 20cm tall. the smaller of the 2 has been sending secondary shoots for four days and the taller one has one big secondary shoot(10cm) and a bunch of smaller ones. the big shoot isnt growing any extra shoots yet, does anyone recommend pinching or topping this shoot or even the tops of the plants? and if so when do you suggest to do it?
i am thinking of running my 400watt light for 22 hours a day on my 2 plants for the next 4 weeks then cutting it back to 18 hours for 2 weeks then on to flowering with a 11 on and 13 off routine? other than cost, can anyone tell me what would the downsides for this will be?

i have noticed the start of a little nute burn. so i have cut back the flooding to every 4 hours. i hope the rock wool doesnt dry out too much.

in the last 2 days both plants have really boomed in hieght. and the secondaries are starting to really search for the light. i will post photos soon.