Too bad I saw this thread so late. Sorry to hear you lost yours. I've got two different Euphyllia sp. in different tanks. Like lots of light and moderate water flow. My hammer is host to a pair of skunk clowns and is doing very well. It stands upright alone, not surrounded by any rock, and has enough water flow to make the hammers sway in the current but not so much flow that it is being blown all over the place.

Now that your hammer has died in your tank, you will definitely see a rise in nitrate from its dead flesh. If you have any mechanical filtration in the tank, remove the filter media right away and clean it, which will help reduce nitrate.

As soon as it was starting to go I suctioned up the flesh that fell off got it out, did water changes, and changed our filter media!

Everything is okay now, without my hammer!