Did you have a particular type of sea star in mind? Serpent stars are pretty hardy. You might want to avoid brittle stars, some can become predatory.
No
chocolate chip stars - they eat corals (but they are bulletproof). A
sand sifting star may not have enough grazing room in your tank.
Linckias might do OK but they are extremely sensitive to changes in pH and specific gravity so in a small tank they often fail.
Red fromias are sized right but they too are very sensitive to changes in pH and specific gravity. How long has your tank been up and running?
Jenn
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LFS Owner:
Imagine Ocean

Just keep skimming, just keep skimming, just keep skimming, skimming skimming! What do we do? We skim, skim, skim!