Diatom Problem

Frigideus · Mar 24, 2026

I've had my tank up for a couple weeks now and I think I have stumbled upon a red-rustlike diatom bloom. I am only asking about this because I set up my refugium last week (kit from algaebarn) and dosed the PNS bacterioplankton that came with the kit. The issue is, I am not sure this was the step I was supposed to take since I have live rock (and as far as I was aware, live rock was supposed to help me skirt around most of the uglies) and my nutrients were already balanced out, but I did not think adding plankton would upset my balance so badly. Is this fine, and will it go away? Or what steps should I take in handling this issue? The residents of my tank still seem happy and healthy but now I just have this awful algae bloom. All advice is appreciated.

Mr. Mojo Rising · Mar 24, 2026

hi, Diatom blooms are completely normal, they feed off the silicates in new sand, they will exhaust the food supply in a couple of weeks and die out on its own. Its not necessarily part of "the uglies" since its tied to the new sand and a very temporary phase. Afterwards, you should never see diatoms again unless the rodi filter gets old. IMO Just let it do its thing for now, good luck.

Frigideus · Mar 24, 2026

Mr. Mojo Rising said:
hi, Diatom blooms are completely normal, they feed off the silicates in new sand, they will exhaust the food supply in a couple of weeks and die out on its own. Its not necessarily part of "the uglies" since its tied to the new sand and a very temporary phase. Afterwards, you should never see diatoms again unless the rodi filter gets old. IMO Just let it do its thing for now, good luck.

Thanks, I mixed a 20 pounds of live sand with the standard caribbsea aragonite stuff so hopefully this issue will iron itself out over time!

Randy Holmes-Farley · Mar 30, 2026

FYI, red sounds more like cyano than diatoms which almost always are golden brown in a reef tank setting.

it's an important difference as diatoms usually fade away without an ongoing source of silicate (such as tap water), while cyano can thrive under a lot of reef tank conditions. :)