Get a soil moisture meter they only cost about 10 bucks or less. You can monitor the Ph too. If you are growing in soil you need to adjust the Ph of the water you give them too. I would recomend you use RO water and add some Cal-Mag plus after you add your nutrients and ballance everything out. Cal-Mag plus puts back in the water nutrients most RO systems remove. Use something like Flora Kleen about every 2 weeks or so and inbetween cycle changes. This will help keep nutrient lock from affecting your plants. A good soak should last you about 3 day's give or take but a good moisture meter is a must. Just watch your Ph and keep it in range.