Fallow periods: Going Fishless

[Humblefish]

Please see this updated information on fallow periods: https://www.reef2reef.com/threads/45-day-fallow-periods.805213/

Jay Hemdal 7/13/2023

​

The reason to go fallow (fishless) is to eliminate a fish disease from your DT (display tank). Going fallow works because you are denying the disease a fish host to feed on, essentially starving it to death.

In order to go fallow you must remove ALL fish from your DT. If just one fish is left behind, even a “disease resistant” species, then going fallow is for naught because the disease will continue its life cycle. Corals/inverts can be left in the DT, as those are not capable of hosting - although some are capable of “housing” the encysted stage of certain parasites for a period of time (see “Fallow Periods” below). It is important to continue to feed your corals/inverts while going fallow, and also put a pinch of flake or pellet food into the DT every 2-3 days to feed nitrifying bacteria in the absence of fish poop. Continue to do everything normally with your tank while going fallow; although you may wish to go lights out if you are running a fish only system (just don’t forget to feed that bacteria!)

Fallow Periods - Below is the general consensus fallow periods for all diseases that require it. In most cases, it is the longest known time period that the encysted stage can survive on corals, inverts, rocks, substrate without a fish host to feed on. The fallow period starts when the last fish is removed from the tank.

• Black ich (turbellarian worms) - 4 weeks
• Brooklynella aka “Clownfish disease” or “Brook” - 6 weeks
• Flukes (monogenean worms) - 4 weeks
• Ich (Cryptocaryon irritans) - 76 days
• Uronema marinum - No fallow period, as it does not require a fish host to survive. It is an opportunistic parasite that strikes when a fish’s immune system has been compromised. Uronema mainly affects damsels (especially chromis) and clownfish.
• Velvet (Amyloodinium) - 6 weeks

During the fallow period, the fish must be quarantined and treated for whatever disease(s) are afflicting them (see links below). Successful treatment is imperative to avoid disease(s) from being reintroduced into the DT:

https://www.reef2reef.com/forums/fish-disease-treatment-diagnosis/189284-fish-diseases-101-a.html

https://www.reef2reef.com/forums/fi...is/189658-treatment-options-my-two-cents.html

Quarantining all future livestock purchases is also very important to avoid having to go fallow again in the future: https://www.reef2reef.com/forums/fish-disease-treatment-diagnosis/189815-how-quarantine.html

After the fallow period has ended, you can return your fish to the DT. I recommend doing it one fish at a time, spread out over a couple of weeks. This will give your bacterial levels time to adjust to the added fish bio-load, and avoid a potential mini-cycle/ammonia spike. I also prefer to add back smaller fish first, so they are established ahead of the larger, more aggressive ones.

Do be sure to closely monitor your ammonia levels while adding fish back. I advocate using a Seachem Ammonia Alert badge for constant monitoring:

Edit: You can also use a FW black molly to test if your fallow period has been successful: https://www.reef2reef.com/threads/fallow-periods-going-fishless.190324/page-2#post-2855190

 

[JVH]

I am In the midst of an outbreak and I set up a QT last night. I will go fallow for min 8 weeks and keep nothing but snails, my 2shrimp and crabs. My question Is tonight I will be putting back the rocks in the DT I took apart last night
to remove the fish and I was wondering If I should remove the sand? Remove forever? or remove and replace with new before fish go back In. Is there a better chance of disease with a BB? I like the look of it but if its adding to disease, I don't want it.. And, I will be upgrading in a few month to get more room to a 60g all in one nuvo. Shall go BB in that? Would love opinions on this subject. AND While Im going fallow is that the time to remove the sand?

 

[Humblefish]

The encysted stage of external parasites (ex. ich) is capable of sticking to rock, sand, corals, snail shells, even the glass, etc. So, removing the sand would only eliminate one form of "temporary housing" for them.

 

[Humblefish]

Please be advised the fallow period for Ich (Cryptocaryon irritans) has been adjusted to now be 76 days. Based upon new calculations (see below):

Let's do the math and tweak the fallow period for ich using the parasite's known life cycle & worst case scenario:

1. Let's say a trophont drops off the last fish you catch before going fallow. We know that the protomont can only crawl around 18 hours max before beginning the encysting process. The process itself takes no longer than 12 hours until it has hardened around what is now called a tomont. 18+12=30 hours, but I'm just gonna call it 2 days to err on the side of caution.
2. The longest known time period it took for theronts (free swimmers) to be released from a group of tomonts is 72 days. However, I want to make it clear that this 72 days has only been encountered once; one study involving a single strain of ich. In most other studies, 7-14 days has been "the norm" for theront release.
3. Once released from it's tomont, a theront must find a fish host to attach to within 48 hours (2 days) or it dies. Thus ending ich's presence in your fallow tank. Although in actuality, a theront's infectivity is greatly reduced just 6 - 8 hours after it leaves the cyst. It's non-infective after just 8 hours, but still able to move for up to 48 hours. So again, to err on the side of caution, we're gonna say 2 days for this "final phase" of it's life cycle.

So, let's add it all up. 2+72+2 = 76 days. That would be the true maximum fallow period for ich. Probably a bit of overkill, but I will make the necessary adjustments to the stickies and start recommending 76 days from this day forward.

 

[robert]

All this is fine if your running a smaller tank with limited stock.

It is absolutely impractical for the person with a large tank and bigger fish. For those - management is the other option.

 

[Humblefish]

For those - management is the other option.

Ich eradication vs. Ich management: https://www.reef2reef.com/threads/ich-eradication-vs-ich-management.188775/

Diatom filter for treating external parasites? https://www.reef2reef.com/threads/diatom-filter-for-treating-external-parasites.212429/

 

[Daniel@R2R]

Excellent write-up, @Humblefish! ...as usual!

 

[edosan]

Right there...fallow almost 1 month 2 months the finish....copepods house
Al fishes are good, and ich free after TTM

 

[Gsxrfl1k6]

Question about the velvet fallow period: I have a shrimp, and a couple of large hermit crabs I've been feeding in a tank that has been without fish for about 3 months. The tank had what I believe to be velvet. The tank has also been lit by LED's as it contains coral as well. I've read that velvet can have some photosynthetic capability and could potentially feed off of non-fish meat (such as the stuff I feed my cleaner shrimp) and potentially negate the fallow period. Does anyone know if this is true? I want to start adding some of these inverts from the tank in question back to my DT and want to make dang sure I'm not going to re-introduce anything to my now parasite-free DT. Thanks!

 

[Humblefish]

Question about the velvet fallow period: I have a shrimp, and a couple of large hermit crabs I've been feeding in a tank that has been without fish for about 3 months. The tank had what I believe to be velvet. The tank has also been lit by LED's as it contains coral as well. I've read that velvet can have some photosynthetic capability and could potentially feed off of non-fish meat (such as the stuff I feed my cleaner shrimp) and potentially negate the fallow period. Does anyone know if this is true? I want to start adding some of these inverts from the tank in question back to my DT and want to make **** sure I'm not going to re-introduce anything to my now parasite-free DT. Thanks!

The 6 week fallow period takes into account it's photosynthetic capabilities. I've never read anything about it being able to feed off of non-fish meat, can you provide a source?

 

[Gsxrfl1k6]

The 6 week fallow period takes into account it's photosynthetic capabilities. I've never read anything about it being able to feed off of non-fish meat, can you provide a source?

Awesome, thanks so much for the reply. I'll have to see if I can find it again. I did so much research and searching around over the last few months it's insane.

 

[edosan]

Almost there, less thank 1 month to finish my fallow period, improving filters for shooting

 

[Brian Kim]

Great write up Humble, thought the new fallow period was 72 days, I will be adding those extra 6 days to my tank

 

[scott021467]

Excellent write up. I am going through a fallow period and this information helped considerably.

 

[edosan]

he he he he 7 days to go..the only ich I have now is in my fingers to add fishes!!!
New additions:

 

[edosan]

remove this one

 

[edosan]

Like humble told me a while ago, fallow was the best thing I did for my reef...not easy...but now I am very happy about it.
I will try to make a video this weekend.

 

[4FordFamily]

Humble is the master but if it were me I would do a full three months. 84 days was not enough for one of my strains. The fish were all put through 2 months of cupramine 2x the therapeutic dose and also FULL TTM. DT got ich when I put them back.

**UPDATE 10/17 — when I moved the tank when I moved in June I discovered why the fallow didn’t work. I had a tiny watchman goby I thought had died that was in the sump. So, the fallow period wasn’t fallow a all. Couldn’t find him in there he was with the live rock and impossible to access or see. Don’t add tiny fish! He must have been sucked up through the overflow!**

Not sure which was the culprit - TTM and cupramine like that not working or a strong resilient strain. Just my .02 based only on one observation. I was very careful to sterilize and not cross contaminate during TTM.

 

[Humblefish]

Longer is always better when going fallow. It's always possible an untested strain of ich exists that can take longer than 72 days for all the theronts to be released from encysted tomonts.

I recently attended a lecture by Tony Vargas (author of "The Coral Reef Aquarium") where he advocated letting a newly setup tank cycle without fish for at least 90-120 days without light; 180 days is even better. His argument had nothing to do with fish diseases, but to let the microfauna on the LR propagate without being eaten by the fish. Doing this alleviates some of "the uglies" many new SW aquariums experience (diatoms, GHA, dinos, cyanobacteria, etc.) The theory is that microfauna present in sufficient numbers inside your aquarium will deal with these problems for you, keeping them out of sight.

So, what does this mean for you if going fallow to starve out a fish disease in your DT? Take the opportunity to add more pods/microfauna to your tank, or stock more CUC if needed. You can even add more corals/inverts during the fallow period, so long as you restart the 76 day clock to compensate for any tomonts which they might be carrying. Turn a negative into something positive and fun!

 

[shoelaceike]

Going Fallow​

The reason to go fallow (fishless) is to eliminate a fish disease from your DT (display tank). Going fallow works because you are denying the disease a fish host to feed on, essentially starving it to death.

In order to go fallow you must remove ALL fish from your DT. If just one fish is left behind, even a “disease resistant” species, then going fallow is for naught because the disease will continue its life cycle. Corals/inverts can be left in the DT, as those are not capable of hosting - although some are capable of “housing” the encysted stage of certain parasites for a period of time (see “Fallow Periods” below). It is important to continue to feed your corals/inverts while going fallow, and also put a pinch of flake or pellet food into the DT every 2-3 days to feed nitrifying bacteria in the absence of fish poop. Continue to do everything normally with your tank while going fallow; although you may wish to go lights out if you are running a fish only system (just don’t forget to feed that bacteria!)

Fallow Periods - Below is the general consensus fallow periods for all diseases that require it. In most cases, it is the longest known time period that the encysted stage can survive on corals, inverts, rocks, substrate without a fish host to feed on. The fallow period starts when the last fish is removed from the tank.

• Black ich (turbellarian worms) - 4 weeks
• Brooklynella aka “Clownfish disease” or “Brook” - 6 weeks
• Gill Flukes (worms) - 4 weeks
• Ich (Cryptocaryon irritans) - 76 days
• Uronema marinum - No fallow period, as it does not require a fish host to survive. It is an opportunistic parasite that strikes when a fish’s immune system has been compromised. Uronema mainly affects damsels (especially chromis) and clownfish.
• Velvet (Amyloodinium) - 6 weeks

During the fallow period, the fish must be quarantined and treated for whatever disease(s) are afflicting them (see links below). Successful treatment is imperative to avoid disease(s) from being reintroduced into the DT:

https://www.reef2reef.com/forums/fish-disease-treatment-diagnosis/189284-fish-diseases-101-a.html

https://www.reef2reef.com/forums/fi...is/189658-treatment-options-my-two-cents.html

Quarantining all future livestock purchases is also very important to avoid having to go fallow again in the future: https://www.reef2reef.com/forums/fish-disease-treatment-diagnosis/189815-how-quarantine.html

After the fallow period has ended, you can return your fish to the DT. I recommend doing it one fish at a time, spread out over a couple of weeks. This will give your bacterial levels time to adjust to the added fish bio-load, and avoid a potential mini-cycle/ammonia spike. I also prefer to add back smaller fish first, so they are established ahead of the larger, more aggressive ones.

Do be sure to closely monitor your ammonia levels while adding fish back. I advocate using a Seachem Ammonia Alert badge for constant monitoring:

Will brook stay around unnoticed on fish?