Critters in shrimp/invert only tank

[Laura]

My planted desktop 5 gallon has CRS and 2 brig snails. I've noticed a bloom of waterborne critters - smaller than daphnia; I expect just the regular critters you get when there is no fish to eat them.

The last time I tried an invert only tank (my sulawesi snail tank) I ended up with hydra due I expect to the extra food for them.

How do other invert keepers manage the population of water borne critters to avoid worse problems like hydra?