Could it be Valonia?
>We have growing in our tank two little bubbles that I can only describe as looking like black pearls. They are very small, growing on our live rock, and they seem iridescent with black and blue depending on how the light hits them. Also, their surface seems very smooth and shiny. >>My first thoughts are leaning towards some sort of algal form. There is a nuisance algae called Valonia, or bubble algae. It’s normally green, but does have the appearance of pearls. >We have a 50 gallon saltwater tank with live rock, two pulsating Xenia, two false clowns, three green Chromis and a sand sifting star fish. We also have two big turbo snails, some red legged crabs (had five, not sure how many now, at least two). We also have a six line wrasse, a feather duster, some kind of big bristle worm that we would like not to have. >>They’re actually rather beneficial, and if you ever experience a population explosion of them, then you know that your husbandry/filtration techniques need reassessing, as
