Heather, I personally don't like growing the "water loving" Phrag species in standing water. In nature, they never grow in stale standing water. During rainy seasons, some species are actually flooded/submerged underwater for a few months with clean water continously flowing through their roots. The same goes for besseae but since they grow on slopes, clean water trickles down and goes through their roots but never standing in stale water.
I know a few professional growers who like growing their "water loving" Phrags in water but they are always changing the water almost everyday because stale water attracts all kinds of problem over a long period of time. Hope this helps, Slippah Sistah!!!