Why is My Hammer Coral Dying?

You’ve got your aquarium set up at home and have populated it with all kinds of life and color, but you’ve decided on one last thing to put the finishing touches: Hammer coral. You’ve done the dip test and it went fine, so your hammer coral goes in the tank.

Fast-forward a couple of weeks and you begin to notice that your coral’s not doing well, prompting the question, “Why is my hammer coral dying?” There are a number of possible reasons from lighting and water flow to unlikely predators or improper water concentrations.

There’s Something About Water

When it comes to the speed of water flow and the elemental concentrations in the water, hammer coral can be pretty picky. If you’re noticing deterioration of your coral, these should be the first things you check.

Water Flow

There are 2 reasons to carefully choose the location of your hammer coral placement: Proper water flow and they can eat other corals. Hammer corals are night feeders, meaning they have small tentacles that extend outward at night and eat away at nearby coral.

The good news is that they don’t seem to care as much for corals in their genus, but unless you fill your tank with Frogspawn and Torch corals you might want to keep them at least 7 to 10 inches apart.

Water flow is one of the main reasons your hammer coral could be dying, though, especially if you notice it on one side. Too little flow and your coral won’t be able to take in the right amount of food, but too fast and your coral might not open at all. 

The sweet spot is a space in your tank with adequate water flow that isn’t directly in the way of any jets, but it can be difficult to find this spot while also keeping your hammer coral away from other corals.

If your hammer coral is dying, test its location to see how strong the water flows around it. It could be that one side isn’t receiving enough of a current or too strong of one. Either way, you might need to shift the corals’ placement.

Water Content

The best thing you can do before introducing a hammer coral into your tank is to let the water in the tank settle for around 5 or 6 months. This will allow natural bacteria to form and the water will be similar to what hammer coral is used to.

Once you’ve placed your hammer coral in the water, consistent water changes are key to their survival. 5 or 10 percent changes every week or 2 weeks respectively will allow your hammer coral to thrive by replenishing elements.

If your coral is worse, try changing out 10 or 20 percent of the water every day to try and flush out anything that could be causing the deterioration. Carbon has been known to have this effect, so if you’re adding carbon to the water immediately stop.

The essential elements in your water are calcium, which will let your hammer coral grow, magnesium, which will add to the calcium in the water, and alkalinity, which balances the pH of the water and keeps the acidity levels down.

If your hammer coral shows signs of deterioration, you’ll want to check these levels and make sure they fit with the normal requirements that a hammer coral needs to survive. Before adding calcium, though, always check the magnesium because that can balance it out.


Corals need lighting to survive in general, but hammer corals are photosynthetic. This means that without proper lighting, they can and will die. If your hammer coral’s deteriorating, you may need to adjust the lighting levels in your tank or the placement of those lights.

Some of the best lighting for corals is in the form of LED or metal halides, but it’s important that you incorporate them slowly. Hammer corals need time to acclimate to the new light sources, so be careful how fast you adjust the lighting levels.

Like the water placement, make sure your hammer coral is in a location that receives enough lighting but in this case direct exposure is necessary. The key is enough light to live without being too intense, which can be tricky to figure out.


It was mentioned earlier but when hammer corals are hungry they have tentacles that reach out and find food, especially from other corals. While the majority, approximately 90 percent, of their food intake comes from photosynthesis, one way around their hunger is to feed them.

Small organic matter, such as krill or shrimp, is fine to drop in with them when it’s time to feed, though make sure none of the pieces are too big. Hammer corals are capable of larger “bites,” but keep the sizes reasonable.

When it comes to the feeding, though, watch out for certain types of shrimp because they might stop being the prey.

Unlikely Predators

One of the common foods for hammer corals is shrimp for their small size and simple composition, but they can be the cause of your hammer coral’s demise if you’re not careful. Shrimp, especially peppermint shrimp, have been known to feed on hammer corals.

While this is a specific instance and doesn’t happen often, just monitor what you put in the tank with your hammer coral and watch for any signs of the hunted becoming the hunter.

Other Causes

Sometimes you can do everything right and your hammer coral can still begin to die, if it opens at all. If that’s the case, it could be a couple of things that have nothing to do with your tank.

One of the biggest reasons is a bacterial infection or some other disease. The good news is that most bacterial infections can be treated with antibiotics that you’ll need to brush onto the wound or infectious location on your coral. 

Most of the time the damage caused by these infections will begin to reverse after treatment, especially if you change the water and keep the nutrient levels correct. 

The other major cause for your hammer coral to be dying is stress. Especially if it’s transferred from another tank or not given proper time to acclimate to new surroundings, your hammer coral can literally die from stress.

That’s why it’s so important to adjust things slowly and give your hammer coral time to adjust. However, more often than not, the leading cause of death among hammer corals has to do with the water flow that was emphasized earlier.


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