The Dreaded Dinos! What To Do About Dinoflagellates

Dinos or dinoflagellates tend to look more like bubbly snot as opposed to slimy cyanobacteria which is often confused to be the same thing. Depending on the exact type you have, they often reduce or disappear at night and then come back when the lights turn on. They are unsightly, compete with corals for space and are a sure fire sign of an imbalance in your aquarium.

Dinoflaggelates on sand bed

The reason hobbyists have to come fear dinos is the fact that sometimes they seem virtually impossible to cure. Thanks to the internet and being able to easily and instantly share your experiences with others, the reef keeping community has produced some paths which seem to work in a majority of cases.

Just like algae outbreaks and cyanobacteria, clearing up dinos is not going to be an overnight process. It will likely take weeks, even months of persistence to completely get rid of it. Let it run its course and take time to celebrate the progress and you will be successful.

Download: A Quick Guide To Overcoming Dinoflagellates

UV Sterilizers Can Be Effective

A properly installed UV sterilizer can be an effective means of ending dinos in your tank all on its own but there are no guarantees. UV sterilization is most effective on the dinoflagellates that break up into the water column at night and disappear, then reappear again when the lights come back on.

If you decide to install a UV, we recommend the Pentair units that define distinct flow ranges to target bacteria and protozoa and a seperate flow range for algae. This is because a UV sterilizer needs to be tuned for your particular aquarium size and desired result.

By slowing down or speeding up the flow rate through the UV sterilizer in such a way that processes the entire tank volume so many times per hour, you can target either "algae and bacteria" or "viruses, parasites and protozoa". It is not possible to remedy both of these ailments with a single UV sterilizer operating at one particular flow rate.

The 25 Watt Pentair UV sterilizer is rated for tanks up to 130 gallons. To target Dinoflagellates (protozoa) in a tank of this size, the flow rate through the UV must be between 478 and 788 gallons per hour (GPH). This will process the entire tank volume roughly every 10-15 minutes to effectively keep free-floating dinos to a minimum.

Dinos on the sand bed

Why UV Sterilizers Don’t Always Work

There are multiple species of dinoflagellates hobbyists can encounter in a reef aquarium. UV sterilizers can only kill what passes through them and if the dinoflagellates species you are seeing in your tank remain on the rock work or sandbed, a UV will be ineffective because they never take on a free floating stage.

Other types of dinos, like those described above that disappear at night and come back again during the day, do have a free floating stage and are vulnerable to UV sterilization.

Hanna Instruments Checker Colorimeter

What Causes Dinoflaggellates?

When dinos appear you should be testing your nitrate and phosphate levels. Most experienced hobbyists will run a full water analysis at the first sign of any problems, even if seemingly unrelated to the parameter being tested. Contrary to what you might think, it is the double zero we are really looking out for.

If both phosphate and nitrates are testing at zero, this is likely contributing to the problem. While not proven, repeated anecdotal evidence points to zero nutrients in the water either cause or trigger dinos.

Nitrate Test Kit Results

The general consensus as to why is that when nutrients are this low, dinos will outcompete beneficial organisms for resources and take over the rock surfaces.

So outside of UV sterilization following this 4 step approach has proven effective against dinoflagellate infestations and remember, patience is mandatory.

Feeding Fish

Step #1 - Increase Nutrients

So the obvious remedy here is to increase your nutrients in the tank which thankfully is pretty straightforward. Decrease efficiency of various filters, increase feeding or simply dose nitrates and phosphate with something like Brightwell Aquatics NeoNitro and NeoPhos.

Brightwell Aquatics

No matter your approach, make adjustments until you are maintaining levels above zero and show up on your home water test kit. NYOS Nitrate Test Kits and the Hanna Instruments ULRP meter are the best options for monitoring these parameters.

Important Note: If you are carbon dosing or using biopellets, it is a good idea to stop. This will allow nutrient levels to rise and some theorize organic carbon plays a role in dinoflagellate growth.

Dosing Vibrant

Step #2 - Beneficial Bacteria Battalion

Step two is now that you are maintaining nutrient levels where other organisms have a fighting chance, it is time to start dosing competitive organisms. In this case, Heterotrophic Bacteria like Dr. Tim’s Waste Away or Brightwell Aquatics Microbacter 7.

Just like cyano, it’s hard to definitively say how these bacterias work but some are believed to starve dinos of nutrition, some likely out-compete with them for surface area or territory and some may even be aggressive enough to consume other organisms.

Dr. Tim's Waste Away

Some accounts suggest a cocktail of different bacteria additives to be even more effective. While we wish a recipe was defined here, nothing has been universally agreed upon and likely will be different depending on the exact dinoflagellates you encounter.

Regardless, repeated evidence shows these bacteria additives to be effective against dinos when dosed correctly.

Siphoning dinos out of the tank with a siphon tube

Step #3 - Physical Removal

Physically remove as much dino growth as possible, as often as possible; preferably everyday until the battle is won. Some types of dunos only live in colonies on the rock and sand so removal means siphoning it out. Stirring it up does not have the same effect.

Other types of dinos can be filtered out of the water column with the use of filter socks or fine mechanical filtration when they break apart during the night. In these cases, changing out your filter socks every morning helps.

Phosphate Levels of Cured Rock

Automatic filter rollers like the Rollermat are effective at keeping dinoflagellate populations down. We recently beat an outbreak in our Red Sea XXL750 aquarium here at the office. It was pulling out so much that we were going through an entire filter roll every few days. In our case, that was only a temporary suppression and once UV sterilization was added to the mix, the tank really turned around.

You can also consider using something like the BRS Reactor with 5 Micron sediment filter, exactly like the first stage in your RO/DI system. This kind of thick sediment filter is built for removing particles like this and will be much more effective.

Blocking light from a reef tank to kill dinoflagellates

Step #4 - Complete And Total Darkness

You should be seeing some progress by now in the way of less growth and you have one last step that will have a major effect on the surviving dinos. Complete and total darkness.

Dinos are photosynthetic and turning off your lights as well as blocking out ambient light for 3-4 consecutive days will effectively kill them back. Use an opaque sheet or some black cardboard or poster board to wrap the aquarium and effectively force a black out period.

Neptune Systems Apex

Past that point, your army of bacteria should really start to dominate inside the tank and continue to be patient. Nothing good ever happens fast in a reef tank but with this overall approach, you should notice a substantial reduction of dino growth in a matter of weeks and complete elimination within a month or two.

Becoming an expert on dinoflagellates in an aquarium is a science project of its own. Likely much more involved than what a first-year reef tank owner is willing to dive into. If you want to learn more, we put together a handy Guide to Dinoflagellates with a round-up research and references. You can also find some great information online as there has been a real focus in the reef aquarium hobby on dinoflagellates and how to get rid of them in the past couple of years.

Scolymia Corals

What’s Next

These last few episodes in the 5 Minute Guide really define what we do here at BRS, making reefkeeping fun and easy for all of you. Going beyond the standard advice and really helping you feel prepared for anything your reef tank can throw at you, specifically when things are not going so great. Episode #28 is also focused on what to do when things go wrong except this time we are talking about corals and what to do if you just can't seem to keep them alive and looking healthy.

5 Minute Saltwater Aquarium Guide Episode #28

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