The Salty Side: Saltwater Aquariums for Beginners

White Spot on Saltwater Fish

White spot on saltwater  fish, the catchy name attributed to the appearance of small white spots that look like salt grains on a fish, and the nemesis of the marine hobbyist. Also known as marine ich, it is one of the most reviled parasites in the reefers world.  It will also be no surprise that it treatment and irradiation are some of the most commonly asked questions on saltwater and reef forums too. with so many fish tank owners looking into ways of how to treat white spot on saltwater fish. 

What is White Spot or ICH?

White spot, also known as ICH, on saltwater fish is caused by the parasite Cryptocaryon irritans, a protozoan that is found in all saltwater habitats.  The most notable symptom of white spot is when your fish start rubbing themselves against the rock scape to relieve the ich that accompanies the infection. Tiny white dots begin appearing on the body and fins of the affected fish, and in a very short period the protozoan will have spread throughout an entire tank, infecting all fish within.  

The reason for its loathing?  It can unintentionally be introduced to a parasite free system not only by infected fish, but also through infected water, live rock, snails, invertebrates.  Once you have it in your system the options for its eradication and are limited.

Stress is THE major cause of an inefficient immune system

A fish needs a strong immune system to fight any type of infection. This includes white spot. There are differing opinions on the ability of a saltwater fish to deal with white spot without the intervention of treatment.

In my own experience, long before I invested in a quarantine tank, I unintentionally introduced an infected Blue Tang into my parasite free tank. Blue Tangs are known as white spot magnets simply because they are more prone to stress than other saltwater fish. The introduction of white spot into my system soon had most of my fish ‘flashing’ against rocks and developing the tell-tail white grains. At the time I knew I had to bolster their immunity to help them fight off the infection. I did so by offering a huge variety of food often, and supplemented with garlic or Beta 1,3 Glucan. I also made sure stress was minimised. Your ability to limit stress to as little as possible will have a positive result on your your fish, whether they are healthy or not.

Stress can be caused by:

  • Removal from the ocean or another saltwater aquarium.
    The majority of saltwater fish are still removed directly from the ocean, and this in itself can be a traumatic experience, as they are netted, inspected, bagged, flown to another country, released, bagged, and eventually end up in your aquarium.

  • Introduction to a new environment.
    A completely new environment will definitely have an impact on your fish as it tries to assimilate.

  • Placing fish with incompatible tank mates.
    This speaks for itself. I have lost count of the number of times I have read of a new fish being bullied by existing tank mates. Although it may eventually settle down, it is never good when trying to keep stress levels low.

  • Insufficient provision of hiding spaces or insufficient space in an aquarium.
    Every fish needs down time to recuperate. This may be to hide on introduction to your tank, or even to have a hiding space every night.

  • An unbalanced, fluctuating system.
    Newer systems that have not yet settled can be a cause of stress with fluctuating levels of alkalinity.

  • The aquarium owner messing with the display tank too often.
    Not a lot of fish are comfortable with there environment being disturbed all the time. Fish create territories from the display in your aquarium, and they feel secure within those territories. Every time you mess in their territory you are stressing them out.

The life cycle of White Spot

The life cycle of Cryptocaryon irritans (seen below) allows us to understand the cycle inasmuch as we understand the life cycle of a butterfly, but doesn’t do much in helping us understand how to completely rid our systems of it. Apart from going fallow. 

White Spot Life Cycle

In a study done in 1994 it was discovered that the adult Trophont leaves the fish host, in this case Black Mollys, in the dark.  Not only that, but Tomites exit the cyst in the dark (Yoshinaga & Dickerson, 1994).

As your tank’s lighting dims, your fish find their hiding places for the night.  As activity dwindles, your fish are therefore easy semi-immobile targets in the dark, waiting for the hundreds of Theronts that have just left a single cyst. 

Can saltwater fish fight white spot without treatment?

All fish have the capacity to fight Cryptocaryon irritans without any intervention.  But they must be in good health with a healthy immune system.  If not, you will be fighting a losing battle. If your fish become lethargic and stop eating you have to remove them from the system and place them in quarantine, or QT.

How to treat White Spot on saltwater fish

A QT tank allows you to treat the fish with products that cannot be used in a saltwater tank as they are toxic to invertebrates. Taking it a step further, this would be the ideal opportunity to remove all your fish from the aquarium and treat them all at the same time. By removing all the fish you have effectively removed the host that allows the Cryptocaryon irritans life cycle to continue. Without fish the protozoan will die out. However, the tank needs to remain fishless (fallow) for a period of 12 weeks.

If however, your fish are still active and responding well to feeding there are several different ways in which to treat white spot directly (with medication), or indirectly (boosting their immune system), giving them the best chance do defeat it.

Click the links below to explore each of the methods reefers swear by when trying to fight and treat white spot.  I mention not only what works but also popular ‘cures’ that are more myths than anything else.  You are then free to make up your own mind as to what methods you would like to try.

Hyposalinity to treat white spot on saltwater fish

Most stockists of saltwater fish keep them in holding or display tanks which have a reduced salt content, with a salinity as low as 1.008.  The reason for keeping the salinity at this reduced level is it has been found that inverts and parasites cannot tolerate such a low salt content.  Keeping the salinity at about 1.008/1.009 is known as hyposalinity, or Osmotic Shock Therapy.

Keeping a fish in hyposalinity conditions for a period of two weeks will kill the parasite, another two weeks will guarantee the white spot is dead.

Hyposalinity treatment cannot be carried out in your display tank as the lower salinity is incompatible with majority of life in your tank, including your corals, and must be carried out in a QT or dedicated hospital tank.

Copper Treatment for white spot/ICH

Copper treatment is by far the most thorough and reliable treatment to cure white spot on saltwater fish. There are a few different brands of copper treatment available on the market, with Cupramine being the top go to product.  All brands have their own set of instructions.  The important thing to remember is that whichever brand you choose to use, it will be highly toxic to invertebrates.  The treatment must be carried out in a QT or dedicated hospital tank.

Like hyposalinity treatment, the period of treatment is 2 weeks with another 2 weeks to guarantee the treatment is a success, with your display tank remaining fallow for 12 weeks.

Copper treatment cannot be carried out in your display tank. It is toxic and will kill your tank!

Seachem Cupramine Copper 100ml
  • Buffered active copper
  • Effective against external parasites
  • For marine and freshwater use

Chloroquine Phosphate - Avoclor

Avoclor is an over-the-counter anti-malarial drug in the UK, used to counter malaria if you’re travelling to countries with a prevalence for the malaria mosquito.

In the UK the pharmacist will ask about your upcoming travels to malaria infected areas in order to hand it over.

It is also another useful tool in the fight against Cryptocaryon irritans.  

Chloroquine Phosphate (CP) can be used either as a drug diluted in a dedicated quarantine tank as a preventative measure, or it can be fed orally to fish displaying symptoms of white spot.

For the purpose of this article we’ll look at oral administration.  Firstly, it has to be acknowledged that CP can be very bitter to the taste and consequently your fish may end up refusing to eat it.  But there have been reported successes with the below recipe.

Mix the following ingredients together:

  • 60ml of gelatine (mix the powder with water to the correct dilution rate, then use 60ml of that mixture).

  • ½ an Avoclor tablet

  • A couple of cubes of thawed frozen fish food.

After mixing, set the mix in a used fish food blister pack and place in the freezer.

As with copper treatment, Chloroquine Phosphate is highly toxic to invertebrates, therefore feeding fish in your display must not be taken lightly.  Feed half a cube at a time, twice a day, and ensure that none is left in your tank.

Having done this myself, I confess that I was very concerned about my cleaner shrimps snagging it from the water column, and any unaccounted for pieces being left in the tank. I prepared by turning off the flow, apart from my return, and fed as normal to ensure I knew how half a block of food would distribute.  Once I was happy that I had minimised the risks, I fed my fish the mix … and they completely ignored it.

If you are lucky enough to have your fish accept the mix, then continue to do so for at least 14 days.

This will cure your affected fish.  But as with most other methods, unfortunately, to rid your tank of the parasite it will need to go fallow for, yes, you guessed it, 12 weeks.

Freshwater Dip is NOT for white spot

There is a mistaken belief that fresh water dips aid in the prevention and/or elimination of the Cryptocaryon irritans parasite.  Fresh water dips do not treat white Spot on saltwater fish.

Fresh water dips are successful in the early treatment of Oodinum genus parasites such as Velvet as well as Brooklynella.  Oodinum attaches to and feeds on the fish skin cells.  Consequently, when the fish is dipped in fresh water it introduces the Oodinum to adverse water conditions and quickly kills it.

Unlike Oodinum, Cyrptocaryon irritans becomes deeply imbedded within the host.  A fresh water dip will simply not penetrate deeply enough to have any effect on the parasite at all.  Trophonts can survive in freshwater for up to 18 hours.

Reef Safe Treatment – Polyplab Medic

In order to explain how reef safe treatments work, it is necessary to touch on a knowledge base in saltwater aquarium keeping that would take far too long to explain in this article without going off topic. I will add a notation against the reference which I hope to cover in a separate article at a later stage.

Treatments such as Polyp Lab Medic do have the potential to work, however its success is hinged on the conditions already maintained in your own tank.

Polyplab Medic is an additive that increases the ORP (Oxidation Reduction Potential)1 in your aquarium. In simple terms it is the ability of the water to clean itself.

ORP is measured using an ORP probe, usually along with a dedicated ozone generator2.
An ozone generator is integrated into a reef system due to its ability to maintain a self-cleaning, disease free environment, including the eradication of Cryptocaryon irritans.

When using Polyplab Medic, you are trying to achieve what an ozone generator does, which is to raise the ORP to a point that is incompatible for Cryptocaryon irritans. This ORP measurement is generally believed to be in the range of 350 – 420mv.
However, most reefers have no idea what their existing ORP levels are. Some may have higher levels and others may have lower levels. This means that the addition of Polyplab Medic may or may not work.
If your tank has a significantly lower ORP, then the addition of Polyplab Medic will raise it, but may not raise it enough to reach the 350mv mark. Conversely, you may already have a higher ORP and the addition of Polyplab Medic may take you over the threshold and consequently work.

This is why there are so many conflicting opinions on Polyplab Medic. It does nothing for some, but has been very beneficial for others.

The only way to be certain it will treat White Spot or won’t is to try it, or test your existing ORP beforehand.

Just starting out in the saltwater hobby? Get your copy of How To Set Up A Successful Saltwater Aquarium ebook today.

This ebook will help to guide you past the mistakes I have made over the years.

UV Sterilizer to control white spot on saltwater fish

The introduction of a UV steriliser into your system can be very beneficial. Namely for reducing the proliferation of algae spore, and killing any waterborne parasite including the infectious stages of Cryptocaryon irritans.

However, this is where its efficiency ends.

The main argument associated with UV sterilises is that they have the capability to kill even good bacteria. Let’s get this out of the way first. Good bacteria are primarily found in and around live rock and sand, in which and on which they proliferate (see the nitrogen cycle). Good bacteria are affected minimally if at all by the introduction of UV sterilisation.

To understand the limitations of UV, you need to consider the mechanics of it.

A UV steriliser is simply a tube filled with UV light. Aquarium water is pumped through the tube at a slow enough rate to allow enough contact time for the light to kill any free swimming parasite or algae spore.
Cryptocaryon irritans free swimmers are known to emerge in their hundreds, from one of many cysts, and from the fish hosts. The likelihood of every single free swimmer passing through the UV steriliser is close to impossible.

UV sterilisation can definitely be seen as an added method to help treat White Spot and aid in the fight against parasites and disease, but should never be relied on as the sole method of control and elimination.

Coralife Aquarium Fish Tank Marine Salt Water Turbo-Twist UV Sterilizer 6X, For up to 250 Gallons
  • Removes free floating algae, parasites and harmful micro organisms from aquarium water
  • Features a unique twist flow design increases water’s exposure to ultraviolet light improving the treatment of unwanted algae and microorganisms
  • For fresh or saltwater applications

Garlic food additive to help against white spot

Okay, this is where things become somewhat murky!  There are two opposing thoughts in the use of garlic – it does work and it doesn’t work.

In 1998 a presentation was made by Kelly Jedlicki at the Midwest Aquarium Conference in Michigan into the effectiveness of garlic against intestinal worms in pufferfish.  In passing she also mentioned a general decrease in occurrences in white spot on saltwater fish.  No more was said, but the foundation had been laid for further speculation.

As an additive in food, you are encouraging your fish to eat.  And in doing so, you are increasing their ability to strengthen their immunity and fight off the parasite.

Seachem Garlic Guard 500-Ml
  • Concentrated garlic supplement
  • Enhances appetite
  • Also contains Vitamin C, a strong anti-oxidant

Garlic however has been proven to encourage fish growth, reduce nitrogen excretion and improve muscle quality.  But the question still remains, can garlic act independently against Cyrptocaryon irritans?  Does it treat White Spot on saltwater fish?

Cyrptocaryon irritans is a parasitic protozoan.  Allicin, one of the active principles of freshly crushed garlic has been proven to be effective in its pure form as an antiparasitic against some major human intestinal protozoan3.  This may or may not suggest that there could be some truth in garlics effectiveness.

It may be that fish fed with garlic become an inhospitable environment for parasitic protozoan, but without clinical tests this would be hard to prove.

Coincidentally, garlic has also been anecdotally attributed to keeping fleas from biting your dog. The suggestion is that the flea doesn’t like the addition of garlic in the blood.
Garlic is also believed to keep mosquitoes from biting you, again nothing proven.

I’ve used crushed garlic juice in defrosted fish food during White Spot occurrences in the past, and as much as I would like to say there was a noticeable difference in the infection, I can’t.
This may be due to the length of time you should feed it for it to become effective, the amount of garlic in the diet being insufficient (and potentially causing immunity), or it just plain doesn’t work.

Without any hard evidence to the contrary, I’m willing to keep an open mind.

Beta 1.3D Glucan to boost immunity against white spot on saltwater fish

Surprisingly, Beta 1,3 glucan is little known in the aquarium market, yet the evidence is abundant as a leading contender in boosting the immunity of fish.  This product really should be a no brainer with every reefer keeping a bottle in their cupboard.

Rather than go in-depth into the benefits here, take a look at this article: 

If I feel my fish could do with a dose I simply open a capsule, pour a small amount of the contents into defrosted food and let it sit and soak in for a while. Then I feed as normal.

This is not a cure for white spot, but should your fish show signs of infection, this would be the first thing I would reach for to help treat White Spot. Beta Glucan Powder (1,3/1,6) - Beta Glucan Supplements - Immune Support Supplement - Fiber Supplement - Beta-Glucan 250mg Powder (100 Grams - 3.5 oz)
  • 🟠 Boosts Immune Health - Beta Glucan, an immune support supplement, is natural compound found in many foods, including mushrooms, oats, and barley. This Beta Glucan Powder, which is a fiber supplement, is for immune health which helps fortifies the body's natural defenses against harmful stressors.* If you're looking for a healthy supplement, Beta Glucan powder is great choice for optimal health.*
  • ❤️ Supports Heart Health - Beta Glucan is natural source of fiber, which is found in many foods including oat . When taken in conjunction with diet and exercise, this Beta Glucan supplement, also a fiber supplement and immune support supplement.*
  • 💚 Aids Healthy Digestion - As a great source of fiber, Beta Glucan helps aid healthy and functional digestion and absorption of food.* Not only that, this Beta Glucan Powder , a fiber supplement, can also help support healthy gut, making Beta Glucan Supplements ideal supplement for overall digestive and gut function.*

Nano Bubble-Scrubbing to control white spot on saltwater fish

Bubble scrubbing has been growing in popularity over the years.  It involves pumping micro bubbles into your display at night using a limewood air diffuser with nothing more than an aquarium air pump.  The diffuser is placed near the return pump in the sump which delivers a fine mist of bubbles into the display.

The premise of nano bubble scrubbing is multi-faceted, some of which can be believed and some a little too presumptuous.

Having used bubble scrubbing for a number of years now, I have come to rely on its ability to keep the water sparkling clean. This is achieved by the nano bubbles attaching themselves to waterborne detritus caught in the display. The detritus rises with the bubbles to the surface and is quickly transported into the weir and through the filtering system.

Lee's 2-Inch Wooden Air Diffuser, 2-Pack,White
  • Precisely hand-cut against the grain of the wood to allow maximum output of super fine bubbles
  • Super-fine bubbles provide increased efficiency in saltwater protein skimmers
  • Available in 2-inch and 3-inch sizes

How do nano bubbles work to treat ICH?

I’m putting my experience out there knowing full well that it would need to be tested under controlled conditions to be confirmed, yet until then it is worth sharing.

A couple of years ago I purchased a baby Regal Tang knowing their reputation for being a ‘white spot magnet’.  Sure enough within a week of acclimatisation it was exhibiting the peppered white spots and flashing against rocks and corals.  Nevertheless it was a healthy specimen, eating voraciously and very energetic.

I’ll reiterate what I said at the beginning of this article, fish have the ability to fight Cyrptocaryon irritans themselves if they have an uncompromised immunity, therefore I monitored the newcomer and was prepared to step in if required due to the Regals small size.  It was the size of the tip of my thumb.

In the same week I introduced the Regal Tang, I also began bubble scrubbing, just to try this new fad out more than anything.  Prior to the introduction of the Regal, I had had white spot outbreaks an average of every six months but had never lost a fish.

Four months went by, and the white spot came and went, then completely disappeared and has never returned.

Logic tells me that without treating all my fish in a hospital tank, and leaving my display fallow for at least 12 weeks that Cyrptocaryon irritans should still be in my tank.  I have done neither and White Spot seems to have vanished.  

This is where you need to keep an open mind…

Cryptocaryon irritans free swimmers are known to leave their cysts and hosts after dark, coincidentally, this is the same time that nano bubbles are run, every single evening.

It is conceivable that the bubbles attach to the free swimmers, disrupting their life cycle and sending them straight to the water’s surface and over weir.

Should this happen every night, repeatedly knocking back the parasites ability to continue its life cycle, eventually it should stand to reason that they could be eliminated.

How to prevent White Spot on saltwater fish

As always, prevention is better than cure so here is the low down on preventing White Spot in the first place.

Invest in a quarantine tank. it does not need to be fancy, but it will save you a lot of heartache in the end. Period.

Unfortunately, most* salt water fish go through a significant amount of stress when removed from the sea, subjected to international freight, and find themselves in holding tanks.  This stress has an undeniable effect on their immune system and their ability to fight any type of disease.

White spot on saltwater fish is also often referred to as ‘stress spots’, in the belief that they are unrelated.  This belief is borne of the fact that when the immune system fights back, the spots disappear.  There is unsubstantiated belief that Cryptocaryon irritans needs to be treated. Therefore if they disappear of their own accord it cannot be White Spot.

*More and more salt water fish are being captive bred, but these still represent a very small percentage when compared to the global market.

Scroll to Top