microscopic view of single dinoflagellate on black background

How To Get Rid Of Dinoflagellates… Once And For All

You Can & Will Beat Dinos!

Updated 2024. You’ve got dinoflagellates in your saltwater aquarium, and you want to get rid of them, but you think it might be impossible.  It’s not, keep reading, follow these steps, and while it may take months, you’ll succeed.

Dinos- those upside-down brown snot-like organisms with air bubbles attached. Perhaps it started slowly with a few snails perishing, but then escalated rapidly, even bothering your corals. Who knows, maybe a fish or two met an unfortunate fate after an ill-fated nibble.

What’s your plan of action? You dive into the internet, only to be bombarded with numerous threads, blogs, and videos, each claiming to have the solution or debunking others. After hours of research, you might end up shutting down your computer in frustration or throwing your hands up in surrender, feeling no closer to an answer than when you started.

Believe me, I understand that feeling all too well! I’ve faced dinoflagellates multiple times and found success through different methods each time.

Here’s the challenge: there’s no consensus in the saltwater aquarium community about why dinoflagellates make an appearance in your tank or how to effectively treat them. To add to the confusion, our understanding has shifted – as recently as 2018, we thought high nitrates and phosphates contributed, but today we believe the opposite is true!

If you’ve been feeling disheartened and on the verge of giving up, this blog is tailored to you. In four sections, we’re going to equip you with the knowledge and motivation needed to regain control and conquer those dinos.

Let’s be clear – there’s no quick fix here. It likely took 2-3 months of suboptimal tank management for the dinoflagellates to take hold, and it’ll take a similar timeframe for them to retreat.

But hold onto hope! You have the power to overcome this challenge. Don’t miss the video I’ve created that outlines my strategy for battling dinoflagellates. I assure you that after reading this brief blog and watching the video, you’ll gain a better grasp of the why and how. Wishing you the best of luck – don’t give up until you’ve emerged victorious!

What Are Dinoflagellates (Dinos)?

microscopic view of single dinoflagellate on black background
© 2017 Encyclopedia Britannica

Rather than me summarizing, here it is direct from Wikipedia: Click here for the original article

  • The dinoflagellates (Greek δῖνος dinos “whirling” and Latin flagellum “whip, scourge”) are single-celled eukaryotes constituting the phylum Dinoflagellata.[5] Usually considered algae, dinoflagellates are mostly marine plankton, but they also are common in freshwater habitats. Their populations are distributed depending on sea surface temperature, salinity, or depth. Many dinoflagellates are known to be photosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey (phagotrophy and myzocytosis).[6][7]
  • About 1,555 species of free-living marine dinoflagellates are currently described.[11] Another estimate suggests about 2,000 living species, of which more than 1,700 are marine (free-living, as well as benthic) and about 220 are from fresh water.[12] The latest estimates suggest a total of 2,294 living dinoflagellate species, which includes marine, freshwater, and parasitic dinoflagellates.[2]
  • A rapid accumulation of certain dinoflagellates can result in a visible coloration of the water, colloquially known as red tide (a harmful algal bloom), which can cause shellfish poisoning if humans eat contaminated shellfish. Some dinoflagellates also exhibit bioluminescence—primarily emitting blue-green light. Thus, some parts of the Indian Ocean light up at night giving blue-green light.

How To Identify Dinos (Dinoflagellates) In your Tank

dinoflagellate algae clumped together on a white sandbed. Light brown in color with air bubbles attached to the end
Dinoflagellates, © Bulk Reef Supply

Appearance-wise, dinoflagellates manifest as brown snot that seems to defy gravity, often accompanied by an air bubble clinging to one end. An unmistakable sign of their presence is the mysterious demise of your snails or crabs. These organisms are particularly toxic to invertebrates, and their presence is dreaded within the aquarium hobby.

In reality, the only foolproof method to accurately identify dinoflagellates is by employing a microscope.

side by side microscopic view of pennate diatom on left and centric diatom on right
side by side microscopic images of an unarmored dinoflagellate on the left and an armored dinoflagellate on the right.

The images displayed above vividly highlight the distinct contrast between diatoms and dinoflagellates. These two varieties of algae are frequently confused by those new to the hobby. The key differentiator, even without the aid of a microscope, is that dinoflagellates tend to possess an air bubble attached to them, causing the algae to ascend towards the surface akin to an underwater stalagmite.

Why Dinoflagellates Show Up In Your Aquarium

Back in 2015, I produced a video – admittedly not a great one – delving into the topic of dinoflagellates. In that video, I expressed my puzzlement regarding the presence of dinos in my tank despite having undetectable levels of phosphates and nitrates. If you’re curious, you can watch that video by following this link, although I believe it has been viewed more times than I’d prefer!

Moving ahead to 2024, we find ourselves with additional anecdotal insights suggesting that dinoflagellates flourish in environments with low nutrients. Thus, my previous belief that having absolutely zero phosphates and nitrates was ideal turns out to be incorrect.

In essence, the reason behind the emergence of dinos goes like this: When nitrates and phosphates plummet to extremely low levels, the population of beneficial bacteria takes a nosedive. This creates an opportunity for dinoflagellates to outcompete the beneficial bacteria for the limited available resources, gradually establishing their dominance.

For a more in-depth understanding, let’s delve into the intricacies of this phenomenon.

1. Too Much Filtration

My focus here is primarily on mechanical filtration, although as you’ll discover in the following sections, chemical and biological filtration also play significant roles.

In our quest to maintain clean tanks and achieve pristine water clarity, we depend on mechanical filtration to eliminate particulate matter. Filter socks, filter floss, poly-filters, sponges, and, naturally, protein skimmers stand out as prime examples of this process.

7 inch white filter sock, new, lying on it's side with opening facing camera
Filter Sock
red and clear pvc protein skimmer with close up of controller for pump.
Protein Skimmer

I was unaware for quite a while that it’s possible to overdo protein skimming in your water! In order to maintain nitrates in your water column, there needs to be a slight amount of matter undergoing decay. This process leads to the creation of ammonia, which then transforms into nitrite, ultimately becoming nitrate. Nitrate is exceptionally crucial, not only for preventing dinoflagellates but also for promoting coral growth and vibrant coloration.

So, if your nitrate levels are consistently reading as zero, consider implementing these two measures:

1. Reduce the frequency of changing your filter sock/sponge.
2. Scale back the usage of your protein skimmer. If you currently run your skimmer 24/7, consider putting it on a timer and using it for 16 hours daily. Adjust the time as needed.

Additionally, be prepared to conduct daily water tests to achieve this balance.

Gear Guide- Protein Skimmers

2. Too Little Nitrate & Phosphate

If the anecdotal evidence holds true, maintaining both zero nitrates and zero phosphates creates an ideal environment for dinoflagellates to flourish. But what leads to nutrients reaching such low levels in the first place? Here are a few common factors:

1. Over-filtration through excessive use of filter socks, roller mats, and protein skimmers.
2. The presence of a substantial refugium with macroalgae that consumes all available phosphate.
3. Utilization of media reactors containing granular ferric oxide (GFO) or similar substances.
4. Abundant biological filtration through a biopellet reactor.
5. Insufficient feeding of the aquarium inhabitants.

3. Not Enough Beneficial Bacteria

This aspect is entirely based on anecdotal observations, as the only way I know of to get sense of your tanks biome is to contact AquaBiomics and submit a water sample.. However, hobbyists have noted a recurring pattern over time: when phosphates and nitrates remain consistently close to zero, dinoflagellates tend to emerge. But why does this correlation exist?

Beneficial bacteria, responsible for driving the nitrogen cycle, require sustenance to thrive. Their nourishment includes decomposing fish food, waste materials, as well as substances like ammonia, nitrite, and nitrate. In situations where these nutrients are lacking, the population of beneficial bacteria diminishes.

The hypothesis revolves around the idea that if the concentration of beneficial bacteria decreases significantly (though we can’t pinpoint an exact threshold), other forms of bacteria and algae could seize the opportunity to compete for the same resources. This scenario could enable cyanobacteria and dinoflagellates to excel as adept scavengers in times of limited sustenance. Consequently, their populations might expand, leading to their dominance within the tank environment.

Explore Beneficial Bacteria Additives Here

colorful infographic of how the nitrogen cycle works
© Bulk Reef Supply

4. Too Much Light

Given estimates of more than 2,000 species of dinoflagellates, the vast majority, if not all of the dinos encountered in saltwater aquariums are photosynthetic. Some species exhibit an incredibly strong photosynthetic nature, to the extent that your tank may appear dino-free in the morning and become engulfed by them by evening.

In my personal experience, an excess of light on its own doesn’t typically trigger a dinoflagellate outbreak. Whenever I’ve had excessively high photosynthetically active radiation (PAR) levels combined with extended photoperiods, I’ve encountered outbreaks of green hair algae or turf algae. However, once dinoflagellates begin their gradual ascent to dominance in your tank, light becomes a factor in their proliferation.

If you’re facing any form of algae issues, it’s advisable to take three steps:

1. Trim down the overall photoperiod, reducing it from, say, 10 hours a day to 6 hours a day.
2. Switch off the green and red LED lights, if possible.
3. Dim the light intensity by around half, if feasible.

While reducing the intensity and duration of lighting won’t singlehandedly solve a dinoflagellate outbreak, it can assist you in initiating a strategy to address the situation.

5. Not Enough Feeding

What’s the simplest approach to boosting your nitrates and phosphates? Feed more! Many of us tend to actually overfeed our tanks. This can lead to elevated phosphates, which in turn can fuel the growth of unwanted algae. Yet, there’s a minority of us, myself included, who are so cautious about preventing nuisance algae that we end up underfeeding. Check out our guide on nuisance algae here.

The truth is, if you increase your feeding regimen, phosphates will likely rise more rapidly than nitrates, and that’s not the most favorable scenario. So, how can you tackle this challenge?

1. Opt for frozen foods that are less nutrient-dense.
2. Consider establishing a macroalgae refugium to assist in phosphate consumption.
3. Alternatively, simply let go of the concern and accept slightly higher phosphate levels!

Hence, if your nitrate and phosphate levels hover around zero, the initial step is to boost the amount and frequency of feeding.

product shot of a blister pack of frozen Hikari mysis shrimp. It has a purple label with a seahorse and coral on it.
Hikari Mysis Shrimp is hands down my absolute favorite frozen food.

How To Get Rid Of Dinos in Your Saltwater Aquarium

Before delving into the details, here’s the fundamental recipe:

1. Maintain nitrates (NO3) between 3-5 ppm.
2. Maintain phosphates (PO4) between 0.07-0.15 ppm.
3. Remove dinoflagellates daily.
4. Administer beneficial bacteria.
5. Reduce photoperiod and light intensity.
6. Elevate water temperature to 81-82 degrees F.
7. Consider incorporating a UV sterilizer.

While there isn’t a universally agreed-upon recipe for completely eliminating dinoflagellates, don’t lose heart! While the aquarium hobby may not offer an absolute solution, there are strategies that appear effective.

Here’s the catch, though: Just as it took your tank weeks or even months to develop a dinoflagellate outbreak, overcoming them will also require weeks or months of effort. If you’re not prepared to face the dinoflagellate challenge every day for potentially several months, then reconsider now, as dinos may prevail.

This doesn’t mean you’ll have to dedicate hours on end each day. However, you’ll likely need to invest around 15 minutes daily in your battle against dinos.

Moreover, maintaining a positive attitude is crucial. Confronting dinos is a lengthy and sometimes exasperating endeavor, filled with obstacles and setbacks. Yet, if you follow our successful recipe and remain resolute, we are confident you can emerge victorious.

By the way, the following recipe focuses on dinoflagellate removal, enhancing beneficial bacteria, and keeping your nitrate (NO3) and phosphate (PO4) levels elevated. You have the flexibility to choose whether you prefer to increase feeding, dosing, or reducing filtration as your primary methods for boosting nutrient levels.

1. Test Nitrates & Phosphates Everyday

Perform joint nitrate and phosphate testing daily, using the two highlighted test kits, which I personally favor for NO3 and PO4 testing.

Understand the patterns within your tank. If your nitrate and phosphate levels are low, you’ll have to implement measures to boost these parameters through dosing, feeding, or reducing filtration.

Dinoflagellates tend to emerge following extended periods of zero or near-zero phosphates and nitrates. To prevent this, employ the following steps we just mentioned to maintain slightly elevated levels of these parameters.

Throughout this battle, lean towards having slightly higher levels of NO3 and PO4, rather than risking insufficient amounts.

2. Maintain Phosphates Between 0.08-0.15ppm and Nitrates Between 3-5ppm

Numerous approaches exist, ranging from increasing feeding to reducing filtration, in order to achieve this. However, if neither of these methods suit you, there’s a third alternative.

You can opt to buy NO3 and PO4 supplements and dose them daily. Various products are available for this purpose, but be aware that consistent testing and dosing are necessary for effective results.

The advantage of directly dosing NO3 and PO4 is that you can bypass the complexities of altering filtration and feeding routines. Let’s face it, when we increase our feeding, phosphates often rise more swiftly than nitrates, leading to unwelcome algae growth.

Conversely, when we decrease filtration, we might experience a sudden upsurge in NO3 and PO4 levels, which could prove challenging to lower later on.

No matter which method or combination you choose to maintain slightly elevated nitrates (NO3) and phosphates (PO4), it’s important to stay vigilant and make daily adjustments as necessary.

If you’re also grappling with other types of troublesome algae, don’t forget to explore our “Beginner’s Guide to Nuisance Algae.”

3. Use Less Mechanical Filtration

This can become a bit perplexing, so let’s break it down. If your recent PO4 and NO3 tests reveal near-zero levels and you’re not dealing with dinoflagellates, then indeed, reducing your mechanical filtration can help stave off dinos. Why? Because decreasing your filter sock changes or running your protein skimmer less frequently can eventually lead to elevated PO4 and NO3 levels (assuming other factors remain consistent). However, here’s the important caveat…

If you’re already contending with dinos, it’s advisable to replace your filter socks, sponges, or filter floss every morning to eliminate dinos. You can still reduce protein skimmer operation to enhance nutrient levels. When it comes to filter socks, sponges, and floss, daily replacements are effective in eradicating dinos from your system.

If your protein skimmer runs nonstop, you might be extracting excessive nutrients from the water column. How does your skimmate appear? Is it a light brown shade? If so, you have what’s referred to as a “wet” skim, indicating there’s more water than organic material. A “wet” skim might imply that you’re removing too many nutrients from the water column.

Therefore, if your nitrates read as zero, contemplate placing your skimmer on a timer for a 12-hour operation or adjusting the water level within the skimmer body itself to achieve a more “dry” skim.

4. Feed More

The simplest way to boost your phosphates and nitrates is by increasing your feeding regimen. This often involves elevating the frequency of feedings. If you currently feed twice daily, experimenting with three or even four times a day could be beneficial. Keep a close watch on your NO3 and PO4 readings daily to guide you on when to adjust your feeding habits.

A brief point to consider about pellet/flake vs. frozen foods: If your nutrient levels are too low, opting for pellet or flake food can aid in raising your PO4 and NO3. Pellets and flakes tend to have higher nutrient content, contributing more food and waste to your system. Consequently, this can lead to increased phosphate and nitrate levels.

However, exercise caution as feeding can sometimes cause phosphate (PO4) levels to rise significantly faster than nitrate (NO3) levels. If this situation arises, you might need to explore alternative methods to enhance nutrient levels in your system.

5. Manually Remove Dinoflagellates Everyday

The most practical approach to reducing dinoflagellates is to extract them on a daily basis. Utilize a gravel vacuum to remove as many dinos as possible each day. Perform this task while your lights are on, as dinoflagellates are most abundant during your photoperiod.

I suggest using a gravel vacuum connected to a filter sock and a 5-gallon bucket. This way, instead of needing to carry out a water change (which could lower PO4 and NO3 levels), you can simply return the filtered water to your system. Rinse the filter sock and it’s ready for reuse!

For scraping dinos off live rock or decorations, a toothbrush can prove to be a valuable tool.

Remember, you won’t achieve an instant victory in this battle. Don’t be discouraged if you find the dinos reappearing the next day. Understand that consistent daily efforts are gradually reducing their numbers, and ultimate success is within reach.

Is this step a bit of a hassle? Absolutely, it is!

6. Remove and Replace Filter Sock/Floss/Sponge Every Morning

I understand that this advice seems contrary to what I previously mentioned about reducing mechanical filtration. However, the objective here is to maintain elevated NO3 and PO4 levels while also striving to eliminate as many dinoflagellates as possible on a daily basis. Given that dinos tend to release and disperse into the water column during the night, they can be captured in your filter sock, floss, or sponge. Thus, it’s beneficial to change these components daily.

Since you’re changing your filter component daily, you’ll need to decrease filtration in other ways. If you’re using a protein skimmer, consider employing a timer to run it for 12 hours a day instead of 24. Alternatively, if it’s possible to adjust your skimmer to produce a drier skim, that’s a viable option.

For those not using a protein skimmer or other mechanical filtration, you’ll need to either increase feeding or directly dose PO4 and NO3.

My favorite wifi strip is no longer available (sad face), but this one from Amazon gets high reviews and I’m sure works just fine!

7. Stop Use of GFO, Carbon Dosing, Biopellet Reactors, and Any Other Nitrate or Phosphate Reducing Media

Here’s the main idea:

  • GFO works by absorbing phosphate, effectively removing it from the water.
  • Carbon dosing accelerates the removal of organic matter by providing more food for beneficial bacteria. However, this approach can be too intense and lead to nitrates dropping to zero.
  • Biopellet reactors have a similar effect as carbon dosing.

For now, consider discontinuing the use of these products and allow your water to accumulate some organic matter.

8. Dose Beneficial Bacteria Daily

Approach this cautiously and remember to test daily. The purpose of introducing beneficial bacteria is to create a competition for limited resources with dinoflagellates. Since both types consume nitrates and phosphates, the aim is to empower the beneficial bacteria.

However, exercise caution. As you add beneficial bacteria daily, they will progressively consume more nutrients. Without careful monitoring, your nitrates and phosphates might plummet to zero once more, allowing dinos to regain control.

Keep in mind that not all bacterial supplements are equal. I suggest using the following:

  • Consider using the following beneficial bacterial supplements:

    Brightwell Aquatics Microbacter 7
    Dr. Tim’s One & Only
    Dr. Tim’s Eco-Balance

    Instead of dosing them all simultaneously, opt for a rotation approach. For instance, use Microbacter 7 on day one, Eco-Balance on day two, and continue this pattern. This strategy prevents overwhelming your system with multiple supplements at once.

9. Raise Tank Temperature to 81/82 Degrees F

Avoid making sudden temperature changes; instead, gradually increase the temperature by one degree each day. While most fish and corals should handle this adjustment well, keep an eye out for any signs of stress, especially among sensitive or cold-water species.

Interestingly, increasing the temperature seems to be effective against dinoflagellates, although the exact reasons behind this are still unclear. Online sources like Reef Builders have discussed the benefits of higher temperatures in controlling dinoflagellate outbreaks.

10. Install A UV Sterilizer

Adding a UV sterilizer to your setup is an optional step, but some enthusiasts have reported significant benefits from using one. Dinoflagellates come in various species, each exhibiting slight differences in behavior within a saltwater aquarium.

For instance, certain types of dinoflagellates tend to vanish entirely during the night, possibly releasing into the water column. This specific behavior makes them susceptible to eradication via a UV sterilizer. However, this approach may not be universally effective for all dinoflagellate species.

Should you decide to invest in a UV sterilizer, ensure that you configure it with the appropriate flow rate. Additionally, consider gently disturbing the dinoflagellates each night, prompting them to enter the water column, flow through a filter sock or sponge, and ultimately pass through the UV sterilizer.

For installing a UV sterilizer, you’ll need the following:

  • UV Sterilizer
  • Pump
  • Flexible Tubing
  • Hose Clamps

Explore UV Sterilizers Here

product shot of small black hang on the back Aqua UV sterilizer on white backdrop
UV Sterlizer

Here’s a video I made in 2023 about UV sterilizers.  It’s a good one actually!

11. Perform a three Day Blackout

Implementing a 3-day blackout can significantly disrupt the growth of dinoflagellates due to their high photosynthetic nature. While a complete 72-hour blackout might not completely eliminate dinos, it can certainly provide an advantage in the ongoing battle against them.

For this method to be effective, you must fully cover your tank to minimize light penetration. It’s important to include an air stone inside the tank and closely monitor water temperature throughout the blackout period.

Can this approach be applied to tanks with corals? Yes, most corals are resilient and can withstand several days without light.

Concerns about feeding the fish within the tank during the blackout can be addressed by feeding them at night when the room is completely dark.

After the three-day blackout, it’s crucial to continue following your dinoflagellate action plan. Don’t be discouraged if you observe some dinoflagellates returning after the blackout – this is expected. However, the blackout might have removed enough dinos to enhance your chances of ultimately eradicating them.

aquarium wrapped completely in cardboard and duct tape
© My First Fish Tank

12. Consider a Hydrogen Peroxide Dose

While I don’t endorse the addition of hydrogen peroxide to your aquarium, I can acknowledge that some aquarists have reported success in using it to combat dinoflagellates. If you’ve exhausted other methods and are feeling frustrated, you might want to explore this approach. You can find more information and discussions about it on this Reef2Reef thread. However, always exercise caution and thoroughly research before trying any new treatment in your aquarium.

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