I have two clowns in my tank. Clowns dont need anemones at all. I dont have one for my clowns. For a tank that size stick with one anemone. What kind of lights do you plan on keeping over the tank? Anemones need lots of light. 30 gallon tank two clowns and a gobies or blenny or something that size would look great!
That is more than enough room under the stand to build a sump. Just be wall to wall for the sump. Put some baffles to keep the bubbles from being returned to the tank and you are set. Here is a pic of a sump that i plan on building soon well within the next month or two. This is just to give you a general idea of what baffles are. You can use this design just make it 20" vs 23"
