Bad Guys
Bad Guys

First thing to note: These are not welcome in your tank, the name kind of gives that away anyways!

For those of us (including myself) who suffer with sever arachnophobia, just about the worst thing you could imagine finding in your aquarium is a spider.

Sea spiders are not like land spiders, they do have 8 legs, but they are not actually related to the land dwellers. There are more than 1300 known sea spiders.

Spider in Zoa
Spider in Zoa

Sea spiders can be very difficult to spot, in some instances they grow to a maximum of 0.4cm, which in a tank full of corals and live rock, makes them very tricky to spot. If you do have them, chances are you will find them dining on Zoanthids or anemones, they are particularly fond of LPS corals and Zoas. Nearly all sea spiders are predatory, and will cause issues in your tank.

They will be easiest to spot if they are amongst your Zoanthids, the Zoa’s polyp will be closed and you may just see some legs popping out of the polyp.

How do you control the numbers?

Sea Spider
Sea Spider

The offence is a good defence when it comes to Sea spiders. Dip all corals before putting them into your aquarium, and where possible, quarantine them and monitor them for at least three weeks before putting them into your main display.

If you have found them in your main display, remove as many as you can manually, and dip the coral every other day for three weeks. This should give any eggs a chance to hatch and for the coral dip to remove any newly hatched eggs.

Do they have any predators?

Sea spiders do have a few known predators. It is important that you carry out research before adding any new livestock to your aquarium to ensure they are compatible with your existing stock, and that you can meet their care requirements.

Copperband Butterflyfish
Copperband Butterflyfish

Known predators include:

  • Butterfly Fish
  • Six Line Wrass
  • Melanurus Wrasse
  • Coris Wrasse