How many do you have? Weve got a BTA and, until recently, a couple dozen colonial hydroids without issue. It's going to be a matter of placement of the anemone vs proliferation of the hydroids.
If you decide you dont like the hydroids anymore, after adding half a dozen bumblebee snails and some emerald crabs, a lot of ours have mysteriously gone missing. We will see if they're gone for real in a few weeks I suppose.