Good Guys

First thing to note: Spirorbid Worms are GOOD guys!

If you are seeing tiny white spirals on your glass, rocks, substrate & even powerheads, you likely have Spirorbid Worms in your aquarium. These tiny spirals will only reach a maximum of 2 – 3mm in size.

Spirorbid Worms are harmless filter feeders. They make themselves a small spiral shell that the worm lives in and pops out to feed, much like a feather duster worm. They thrive off of powdered coral foods, phytoplankton & other small powder like substances, but they will also feed on uneaten fish foods, detritus & fish waste.

Spirorbid Worm
Spirorbid Worm

If you are just starting to see these critters, it is a good sign that your tank is maturing. They seem to bloom initially, but will eventually control their own numbers once your tank has a bit of age to it & isn’t so nutrient rich.

But, while they are harmless, not everyone wants to see them all over their glass or rocks…

How do you control the numbers?

Tiny white spirals on back wall of reef tank
Tiny white spirals on back wall of reef tank

Firstly, you should reduce the amount you are feeding, particularly if you are feeding coral powders. This will significantly reduce the amount of food available to the population. You should also consider defrosting any frozen foods and throwing away the liquid, again, it’s all about reducing the number of food particles in the water column.

Another option is manual removal. You can simply scrape them off of the glass or any other part of the aquarium you don’t want them on.

Do they have any predators?

There is no reliably known predator for Spirorbid Worms, but some people have seen some success with the following:

Sixline Wrasse
Sixline Wrasse
  • Hermit Crabs – the hermits are thought to pick them off any rock work they find them in.
  • Six Line Wrasse – Be careful if you choose to go down this route, Six Line Wrasses don’t have the best reputation for playing well with their tank mates & there is no guarantee they will eat the Spirorbid Worms.
  • Peppermint Shrimp – again, these are thought to pick them off the rocks, but they are not known to actively hunt them down.