Tank Transfer Method vs Marine Ich (Cryptocaryon irritans)

by Jon Slomski

The Tank transfer method has become one of the most widely used way of eradicating marine Ich. We use this method for both infected fish and as a prophylactic treatment for all new arrivals to make sure they are not infected before adding them to your display tank. To understand how this method works, it is key to know about the biology and life cycle of the marine ich parasite.  We will try to outline both so that you have a complete arsenal to deal with and hopefully eraditcate marine ich from your fish and fish tanks!

What is Marine Ich?

Marine Ich is one of the most common ailments of fish that are kept in captivity, the other being marine velvet.  Marine ich is actually a parasite that has 4 life stages.  These life stages are devilishly clever and once you understand them, you will see why this parasite is so much more common with captively held fish than in the wild.  In the wild, Marine ich is not a problem for a few reasons.  First, fish’s immune systems are much stronger in the ocean than when they are captured and shipped across the world to our local fish stores. This reduced immune system reduces the fish’s ability to fight disease and parasites.  Second, there are predators like shrimp and cleaner wrasse in the wild which help pick off and reduce the density of the “white dot” phase of Marine ich.  Finally, in the ocean fish don’t always bed down in the same location.  More on why this is important in a bit.  Let’s take a look at the 4 life stages of this parasite, each of which has a crazy name to go along with their devious plan.


1-The Trophont stage is when the parasite is actively feeding on the fish. This stage last for 2-7 days and shows itself to us as the common white dots on the fishes skin, gills, and fins.
2-The parasite then drops off the fish and swims around finding a place to encyst. In this phase, it is called a Protomont.  An important piece of information here is that it must find a crevice in rock or gravel between 2-18hrs after dropping off the fish or the protomont will die.

3-Once the free swimming Protomont finds adequate substrate it will en-cyst and multiply in the cyst for 3 to 28 days.  This stage is called the Tomont stage and some argue that they can stay in this stage for up to 72 days.

4-Once the parasite hatches from the cyst it is called a Theront and has 24 – 48 hr to find a host or it will also die. In captive tanks, we see fish typically bed down in the same spot every night and after seeing how these stages work, its easy to see how a fish can get just nailed by these little buggers as they go through their life cycle.

Tank Transfer Method Explained

The Tank Transfer Method or (TTM) takes the information on the life stages above and uses it against these parasites to eliminate them from your fish in about a week.  This is good for new arrivals only as established tank treatment requires the removal of ALL fish for a period of at least 60 days to be sure all the life cycles have run their course.

Items for the TTM include,2 tanks are needed (I use 5 gallon buckets for fish under 5”), 2 heaters, and an air pump. I use 100 watt or smaller heater to make sure the water temp does not get too high.  The reason for the 2 buckets is to eliminate cross contamination which we will explain here in a bit.

First, set one tank up with new salt water, making sure to match temp, salinity and PH of the tank the fish are coming from. We will refer to this tank at QT1.  Next, place infected or newly acquired fish in QT1. This tank will be free of all parasites so there is no risk of re-infection for at least 3 days due to the life cycle of the parasite. Make sure to test daily for ammonia while fish is in the QT in order to keep them healthy.

Tank Transfer Method


Then, on the 2nd or 3rd day it is time for your first transfer. Simply set up the second QT (QT2) using the second heater and the second air hose with brand new salt water. Do not use any equipment or water that was used in the first QT. Once parameters are matched , remove fish from QT #1 and place in QT #2. During transfer, make sure to only move the fish and no water from QT1 to QT2. Allow QT1 and all equipment to dry for no less than 24 hr before using again when you do your third transfer.  Repeat transfer every 2-3 days for 12 days and your fishies will be ich FREE!

Additional Notes:

**If transferring every 2 days then 5 transfers for a total of 10 days, if transferring every 3 day then 4 transfers for a total of 12 day is necessary. I prefer ever 2 days for 10 days.

**You can also choose to treat with Prazipro during this time to help the removal of other possible infestations.

How Does The Tank Transfer Method Work?

Because the parasite is only on the fish for 3-7 days (they drop off in the tank or bucket) they have no substrate to borrow and encyst into. This break in their life cycle kills the ich and leaves your fish healthy and ready to be introduced or return to your main display tank.

We mentioned earlier that the TTM is mainly for newly introduced fish, but what do you do when you have noticed fish with ich in your main tank that contains gravel and live rock?  In this case it is unfortunately necessary to remove ALL your fish from your main tank, put them in a quarantine or hospital tank for at least 60 days while the marine ich life cycle runs its course.  In this situation, you are breaking the life cycle between the Theront and Trophont phases by not providing a host for the Theront to latch onto.  The reason for the 60+ days is that the encysted Tomonts can remain dormant for a pretty long time in your gravel and rock work.  60+ days should give them time to hatch and die.

Hopefully this was a helpful summary on how to deal with marine ich effectively and economically in your aquarium.  There are many “in tank” treatments available on the market and we have tried them all.  Not a single one has seemed to have any effect like the above method.  It seems that learning a bit about the how the parasite lives is most effective in eradicating it.  If you have any variations or additional steps that you employ, we would love to hear about them!

Jon Slomski has been a member of the ReefNation team for 3 years now and has over 12 years of experience maintaining saltwater and reef tanks.  He is a contributing writer to Reefnation and many other online forums in the reef aquarium hobby.  If you would like to shoot him a question, please email him at:

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