Mini carpet anemones are the smallest one out there. They are great for a nano tank as they dont sting anything, they love to eat, if you get a kick out of seeing animals eat. But they also dont need to be spot fed. I have honestly never seen one disintegrate/ die. if they are not happy they will bleach out but are easily recoverable with feedings. and best of all they stay quarter size. I have seen nanos with the mini carpets and some sexy shrimp. Now that makes a really cool and interactive nano/species tank.
What else will host a clown? I downgraded to a 12G aquapod and kept my old clown. I thought I read somewhere that some LPS will host or more that the clown will choose the LPS, ???
I have found my clowns would host anything that sways in the current of the tank. I have seem clowns host frogspawn, hammer corals and even xenia if a anemone isn't present in the tank.
I now house a rose anemone so they stick to that now
My clowns ignored frogspawn and hammer and are now very happy in anthelia with occasional forays into the hairy mushrooms.
btw - I have to clear out the anthelia every once in a while so if you want to try - lmk. Great for low light, but you have to watch it, not as invasive as xenia, but a fast grower.