i have the same thing but really bad. it clogged one of my ph
's and burnt the motor. even if you keep the lights off it still grows. it started on my rock and spread to the glass. eventually it will start collecting in the water and get moved around by the ph
's. doesnt seem like it settles. ive done plenty of water changes and that doesnt help either. i gave up trying to fight this. im just gonna let my snails and starfish live...when they die im takin down my tank. its been one headache after another.
I posted this problem a few days ago and got no replies. dony think anyone knows what it is.
I hope you have better luck battling this than I did.
funny thing is nothings dead in my tank and my ammonia is also .250
I only have 4 astreas/2 conch/3 turbo snails and a sand sifting starfish.