Hi. Your Phrags can be watered every day when they will receive the oxygen they need to survive, from the fresh water. Please go very easily on the fert because Phrags are not heavy feeders. I keep all my phrags and a few paphs on a continual water supply. The paphs that are watered too much will develop root rot (soggy and soft) but surprisingly my paphs on continual watering are doing great. IMO they survive because the continual supply of H2O doesn't allow any salt build up or stagnation to develop in the media. I'm sure people more experienced than me can find faults with this system---- but what works doesn't need fixing' The very best of luck to you and may all your efforts produce some beautiful blooms.