The Cryptic Nature of Quarantine

How does one quarantine fish? It's a very simplistic process, with some not so simple aspects. Basically, you take a fish home, and after acclimating it (see our acclimation article), you house it alone for a long enough period for the most common infectious agents to go through their life cycle and die off. The problem with this concept is that most of these infectious agents can re-infect their host, and so in order to be effective, something about this quarantine process must interrupt their ability to do so.

Likely the most common fish ailment out there is called Ich or Whitespot Disease. It's caused by a protozoan in the Cryptocaryon genus. There is a lot of information Cryptocaryon on the internet, including vast amounts of peer reviewed scientific literature. Sadly, there is also a massive amount of misinformation about it, which is rife on forums. Most of these misunderstandings come from a very basic misconception, and that is too many people assume that there is only one strain / species of Cryptocaryon (also known as White Spot Disease or Ich). The truth is that no one has a good number for how many strains of this one aquarium problem there are, and there are a least dozens. This being said, the most common of these (and the most well studied) Cryptocaryon irritans.

Crypto goes through several life stages, which is important, because some of these stages are nearly impossible to kill / remove, and other stages are very susceptible to a variety of control methods. The stage everyone can see on the fish that looks like fuzzy little white spots is called a “Trophont” and this is difficult to treat, as it is actually embedded within the skin of the fish, and thus resistant to medications, salinity shifts and most everything else we throw at it. At the Trophont stage, Crypto is feeding on your fish. The best defense against this stage is a very healthy fish (low stress, excess of excellent food).

After the Trophont stage it goes through free stages where it doesn't need a host. These stages are where the Crypto can most easily be removed. The first stage is called “Protomont” and is kind of an intermediate stage where it floats down to the substrate and will “encyst” itself. Protomonts can be removed from the water column, and or killed by some medicines or by UV / Ozone sterilization. However, the window in which they can be killed off here is short, generally less than 24 hours.

Once encysted, they are called a Tomont, (the second free stage) and are very hard to kill during this stage. The way to best interrupt the process is to have multiple quarantine systems. However, this is very laborious, expensive and stressful to your fish. Bascially one would have to move the fish from quarantine to quarantine every two or three days, and completely sterilize the tank the fish just moved out of as encysted Tomonts can live through a plethora of things that should kill it. In basic terms, this Tomont is basically an egg, and inside the egg it's dividing itself over and over again to make new baby protozoans called Tomites, and each egg will carry hundreds and even thousands of them.

These Tomites develop into the third free living stage, called a Theront. This stage is free swimming and infectious. Some strains of Crypto are susceptible to low salinity at this stage, but often the salinity that effects them is also too low for your fish. This salinity aspect is why people usually run their quarantine systems at a salinity lower than seawater, usually 1.019 – 1.021. This doesn't hurt but isn't a cure-all by any means. Thereonts are important because they are also easily removed from the water column.

While that seems like a lot of information, it can really be boiled down to this statement: Crypto goes through stages. These stages take weeks (and depending on strain and temperature, maybe months). Some of these stages are nearly indestructible, and some are not. To have an effective quarantine process, steps must be taken to eradicate Crypto when it is vulnerable (when it isn't in the fish, or the cyst).

On a related note, totally healthy and normal looking fish can be a host for Cryptocaryon without ever showing it, and this can last for months if not years. The encysted stage can live that way for similar time frames, and maybe longer. There are aquariums everywhere that have Crypto, but also have very healthy fish in low stress environments, and thus the fishes immune systems are able to cope well and keep the ailment at bay. We bring this up, because if you decide to quarantine your fish, you have to do it from the start. Meaning, the first fish you buy, has to be quarantined before you ever put it in your tank. Or it could infect the fish that come after it.

With small enough fish, a quarantine system could be as diminutive as a 10 gallon aquarium, but they don't need to be an aquarium at all. If you take the time to interview all of the hobbyists among the staff here, you'll get a long list of vessels used for quarantine purposes; the list is full of things like buckets and big tupperwares, food grade 5 gallon buckets came up more than once. All you really need is something that holds water, and doesn't absorb medication / or leach chemicals. A staff favorite is the food grade cambro tubs available at many restaurant supply stores.

Filtration is important in these systems, though they will be very dependent on water changes to maintain water quality. Then you just need a filter; hang on back filters work well for this, as do sponge filters. People also often use canister filters, even though they are harder to clean, they have one major benefit, this is that you can use their pumps to also move water through a UV sterilizer. If you're going to go through the effort of quarantine, a UV sterilizer is a must. Water goes through your filter, and then goes through the UV Sterilizer, killing and mutating all the free living stages of the Cryptocaryon (and other ailments). If you aren't using a canister, then buy a small pump to feed a UV unit. For the vast majority of display aquariums, we also recommend UV sterilization for a myriad of benefits, see our recent article on UV. If you don't take this advice, then you will need to rely on medication to treat your quarantine, which is a whole other ball of wax (and another article). Just do the UV, and make your quarantine worth the time you took. All of the fish that hold here at Quality Marine are held in tanks that feature UV and Ozone sterilization, and are independently plumbed; we quarantine fish for our public aquaria partners in tanks that have heavy (to the point of redundant) UV sterilization for this very reason!

The only other real concerns in building a quarantine system are cover for your fish so they can hide and feel safe, and making sure the temperature is stable and within range. Temp is easily dealt with as long as you are in a cool area and only need a small heater. Often times the heat generated by the pumps is good enough. In regards to cover, we recommend pieces of PVC pipe. Just pick a size that is big enough for your fish to swim through, cut it to length and sand the cut edges down to round them off.

The last question about quarantining fish is one of length. How long does this process all take? A quick scan through the internet, will tell you than 21 days is a magic number for the elimination of all that is bad for your fish. It isn't. Each step of this life cycle can happen at different speeds based on the strain / species of Cryptocaryon and the temperature of the set up. This being said, the vast majority of the strains we've seen information on will go through their life cycle in four to six weeks if the tank is held at 75 – 80 degrees Fahrenheit. Going longer than this is likely going to be ineffective because the strains that don't go through this process in six weeks, might take years, and there just isn't good information on these yet.

To quarantine or not to quarantine? Really, if you can, there is no question. For just about anyone with an aquarium, it makes sense to set up a small quarantine tank. They are easy to set up and maintain, don't cost much and while not fool proof, are usually a good idea in regards to preventing diseases from getting into your tank. This being said, if you aren't going to go through the effort and expense of adding a UV unit to your quarantine, the process of merely holding fish in another location isn't going to magically remove any illness they have. You'll need to be proactive and attack the crypto where they are vulnerable. Quarantine tanks do also offer an extended period to watch your fish and look for signs of issues with them before they can dive into the rockwork of your main display tank, and this can be handy. Head to your LFS, always ask for Quality Marine fish, and utilize a TMC UV sterilizer on your quarantine tanks and main displays!