Ahh, at first glance the center "thing" looked like an upside down M. doreensis, so my mistake
With that tall of a tank, getting a rock dwelling anemone would be your best bet.
Your current light wouldn't support any hosting anemone. Some quality T5s (( fixture needs to be quality too )), would work, or some of the better LEDs.
Skimmer would really help.
Would wait at least 4 more months, tank isn't mature enough to handle an anemone. Do wonder about that cartridge filter being enough -- anemones put out a decent amount of waste.
The SG should be 1.0256.
Are you using RO/DI water? If so, what is the TDS.