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7 Reasons You Have Brown Zoanthids And How To Fix It!

Zoanthids are definitely one of, if not the most commonly kept type of coral in the world right now and with the number of people getting into keeping reef tanks, the popularity of zoanthids is constantly increasing.

Although zoanthids are classed as a “beginner friendly” coral, they do usually still need you to have some experience within the wider aquarium keeping hobby to be able to maintain steady and consistent water parameters.

Due to people seeing zoanthids listed as beginner friendly, a number of people who are brand new to the aquarium keeping hobby often add them to their tank or setup a zoa only tank and then end up having problems.

One of these problems that seems to be causing more and more issues for people is their zoanthids turn brown so we have noticed a number of questions about brown zoanthids recently so we wanted to publish this article going over the topic.

Why You Have Brown Zoanthids!

Here is our short list of the most common causes of brown zoanthids that you may be having problems with in your tank:-

  • You Have Pandoras!
  • Problems With Nitrate Levels!
  • Issues With Water Temperature!
  • Water Flow Issues!
  • Tank Mates Nipping The Zoa!
  • Lighting Intensity Problems!
  • Zoa Pox!

We will be covering al of these in our article below in more depth but our article going over why your zoanthids are drying may also be worth checking out too.

You Have Pandoras!

Pandoras are a type of zoanthids that have a brown to gold color with these being a very common and popular option for zoanthids due to their low price.

Although Pandoras are meant to have a brown tint to them, they often cause people new to keeping zoanthids in their tanks to reach out worried about why they can see brown on their zoanthids.

In addition to this, Pandoras can grow at a rapid pace and can quickly spread in your reef tank with ease often adding more confusion.

As the Pandoras in your tank start to grow it can give the impression that more and more of your zoanthids are turning brown but it is just this specific type of brown zoanthid spreading in your tank.

Problems With Nitrate Levels!

Zoanthids are very sensative to the nitrate levels in their tank with most types of zoanthids not being able to tolerate nitrate levels above 10 ppm for any significant period of time.

When you start to see your zoanthids turning brown it can often be an indication that the nitrate levels in your tank are too high with this usually being the case if you have recently added zoanthids to your tank.

If the nitrate levels in your aquarium are too high it can add stress to your zoanthids and this will often lead to them shedding their tissue which can result in browning of the zoanthids.

In addition to turning your zoanthids brown, you will also notice an effect on your zoanthids growth rate if your tank does have problems with nitrate levels.

Issues With Water Temperature!

One of the main things that people need to remember when it comes to keeping zoanthids is they are a tropical coral and as such they do require specific water temperatures.

The vast majority of zoanthids do best when kept in water temperatures between 74 and 82 degrees Fahrenheit with a few outliers like certain red zoanthids doing best in water that is a little cooler.

If the water temperatures in your tank starts to drop outside of this range you will often see problems with your zoanthids as they are not used to these cooler conditions.

One of the most common issues that you will see when the water temperature starts to drop is your zoanthids will start to brown and they may also start to release their zooxanthellae too.

Problems with water temperature in your tank can also cause issues with your zoanthids not opening as well as zoanthids melting too.

Thankfully, it is easy to check the temperature of your aquarium water and correct it and provided that you make the required corrections soon enough, your zoanthids should be able to make a full recovary and return to their normal color given time.

Water Flow Issues!

Water flow is very important in a reef tank and it is something that you need to make sure is just right for the animals and corals that you have living in your aquarium.

Zoanthids usually require a moderate water flow in their tank but in some setups they can work in a low water flow setup too without having any issues but this will usually require some prior coral keeping experience on your part to keep a healthy zoanthid in a low water flow tank.

If your tank has high levels of water flow then it can cause problems with your zoanthids that can then cause them to start turning brown.

This can be a serious problem if you have randomly chosen the corals, anemones, and fish that you have in your tank and some of the inhabitants of your tank need high water flow.

If everything in your tank needs a moderate water flow then you can usually just adjust your water flow as required and in time, your zoanthids should recover from looking brown and return to their normal colors.

Tank Mates Nipping The Zoa!

One of the most common reasons for zoanthids turning brown is due to nipping from tank mates.

This can often be easily remedied by just removing the offending fish, shrimp or snail from your tank but in some cases, you may need to take more drastic action like removing all of the zoanthids from your tank and starting over again.

If you have just added a fish or coral to your tank and you start to see the zoanthids turning brown then it is often a good idea to remove that fish or coral from your tank as they are the most likely cause of the problem.

It is usually easy to confirm the problem though as you can usually just watch your tank for a little while to see what is nipping your zoanthids.

In some cases, you will be able to see the little bite marks in your zoanthid too helping to confirm that this is the problem.

Lighting Intensity Problems!

Zoanthids tend to do well in tanks with a range of different lighting intensities but if the lighting intensity is too high or your zoanthids are too close to the lighting source then they can end up turning brown due to heat burns.

This is usually an easy fix as you can usually just reduce the lighting intensity in your tank or change the placement of your zoanthid in your tank to prevent the issue.

Unfortunately though, burns on your zoanthid may not fade and the coral may have these problems indefinitely.

Zoa Pox!

Rather than going over zoa pox in detail in this article, we will just link you to our dedicated article going over zoa pox.