Fireworms can be saltwater aquarium nightmares…here’s what you can do about them

What grows up to 24" and eats all your inverts?

What grows up to 24″ and eats all your inverts?

Generally speaking the Polychaete worms we know as Bristleworms and their stinging bristled cousins the Fireworms are beneficial hitchhikers into a saltwater aquarium that feed off detritus (making them detrivores) and uneaten food helping to breakdown waste in your tank. Not only that, they also aerate the substrate and are very effective nutrient recyclers.

Nice or Naughty?

Typically there will be many small individuals in your tank and you just don’t notice them because they hide in the substrate during the day then come out at night when it’s dark. Normally your Bristleworm population will be self-limiting over time due to the small amount of available food.

Usually they will not be present in enough numbers to be problem unless there is plenty of uneaten food to build their population up. They eat a lot and will grow and reproduce rapidly when there is enough food available for them to do so, this is when problems occur. But unless your tank is over-populated with Bristleworms and/or your invertebrates are being attacked just let them be, because they are doing good for your tank.

Where Problems Begin…

The Bristleworms that cause most of the problems in our tanks are the larger carnivorous Fireworms of the family Pherecardia (Pacific), Hermodice (Caribbean), and other related species which are also effective predators, so when they get large enough they can quickly turn their jaws to your marine pets. Their body spines can inflict a painful sting so handle with caution (this is how they get their name).

If well feed it is not uncommon for Bristle/Fireworms to grow up to 24 inches in length (they sometimes appear smaller than they actually are because they are bunched together and not stretched out to their full length). Fireworms this large can turn into very nasty predators and have ravenous appetites.

They are well known to snack on Anemones, hard corals, gorgonians, Snails, Shrimp, even small fish! Large hungry Fireworms can do a lot of damage in a saltwater tank and you will need to get rid of them.

Detecting a Fireworm…

If you suspect Fireworms of attacking and gnawing on your invertebrates the only way to really tell is at night time a few hours after you have turned off the tank lights, ensure the room has been in total dark for a few hours too. The most effective way to spot them is with a red light (just secure a piece of red cellophane onto the light emitting end of your torch) searching the tank slowly with no rapid movements. Red light will not cause them to hide away like normal light does. Injured corals and anemones can also indicate you have a Fireworm problem.

So, Now You Know You Have Them, How Do You Get Rid Of Them?

1. Prevention:
The best form of defence is always to prevent the problem in the first place. Fireworms are usually introduced to a tank by hitchhiking on Live rock. Before putting the live rock in your tank try laying it out on newspaper. By doing this you should be able to see any fireworms crawling around or sticking out of their holes, remove them with tweezers. Dipping the live rock in fresh water will also help to kill any Fireworms you have not detected.

2. Natural predators:

Sixline Wrasse

Sixline Wrasse

Before I go into natural predators as a solution, please ensure you select a species that will be compatible for your tank and will not starve when all the Fireworms are eaten. It’s also important to note that most of the following will end up eating all your beneficial worms as well:

Arrow Crab (Stenorhynchus setrcornis)
Bird Wrasse (Gomphosus varius)
Coral Banded Shrimp (Stenopus hispidus)
Dottybacks
Maori Wrasse (Cheilinus oxycephalus)
Mexican Red Legged Hermit Crabs (Clibinarius Diguetti)
Mythrax Emerald Crabs(Mithraculuc Sculptus)
Six-Line Wrasse (Pseudocheilinus hexataenia)
Skunk Cleaner Shrimp (Lysmata Amboinensis)
Sunset Wrasse (Thalassoma lutescens),
Wrasses of the Halichoeres family

My personal favourite here is the 6-line Wrasse because it looks very pretty and it is quite active with cool personality.

3. Trapping:
Trapping is probably the most effective method of getting rid of Fireworms but it also requires a lot of patience, as these worms can prove quite elusive and hard to trap. People seem to have limited success with commercial traps, as they tend to trap the smaller worms and not the biggies that cause all the damage and cant be adjusted as easily as homemade ones as the opening ideally will be slightly smaller than the diameter of the Fireworm you want to catch. Commercial traps also can be expensive.

Traps usually work by putting in small pieces of bait (2x pea sized raw salmon seems to work best but any seafood flesh should suffice as long as it is fresh and not frozen) in an area where you know to be a Fireworm and leaving the trap overnight. You may need to try over a series of a few nights changing the type of bait to catch your worm(s).

A homemade trap that has good results is to use a small opaque food container (so the worms cannot see the food) with a tight fitting lid. Cut an “X” in the lid with a razor blade that is slightly smaller than the diameter of your worm, push the 4 sides in slightly do they face down at 45° making escape all but impossible. Immerse so is full of water and leave for 48 hours, if you have no success try different raw seafood bait for another 48 hours. If you believe the worm escaped try with a smaller opening.

4. Substrate breakdown:
This can be a good solution for a severe infestation. This option is a lot of hard work and involves taking out every piece of rock (as above putting it on newspaper and checking and removing fireworms with tweezers) one by one. Also small lots of substrate should be removed and sieved through by hand (or swirled up by hand in a container of water whereby the Fireworms should be able to be netted). Keep live substrate moist with saltwater at all times.

I hope this will help with the presence of nasty Fireworms. Remember the first line of defence should always be prevention!

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