My hammer was my second coral, it seems to be pretty easy. I only have a 2 build HO
t5 and I have seen steady growth. I added it to my tank when it had been up for about ~3 months. My main recommendation is to find the right amount of flow for it. Mine likes pretty low flow, when it is just right you can get some pretty good extension. They are great corals and good growers.
Here is mine the week I added it
And here it is today
That is about 6 months growth.