What is your current water parameter

PH ?
KH ?
NO2 ?
Ammonia ?
Salinity Level (Salt content) ?

You don't have a skimmer? You don't have a liverock? These two are important for long term. If you only rely the filter, it is not enough, at least put some liverock inside your tank.

Any picture of your tank?

For coral without a chiller, there is no guarantee it can survive for long. I think there are a type of anemone not require cool temperature, just require bright lighting and good water parameter. It cost RM 10 only.