Ich Fallow question

[DrBoxedWine]

Hi Everyone,

I have a question regarding Snorvich's post on Ich fallow periods. The info i'm wondering about is this:

These percentages are known as the "empirical rule". What this means for Cryptocaryon irritans is that leaving a tank fallow for 3 weeks will give you a 68% chance that you have eradicated the parasite, leaving a tank fallow for 6 weeks will give you a 95% chance of eradication, but if you want 99.7% chance, you will leave the tank fallow for 9 weeks. That is the reason you see different numbers being used on Reef Central and in the literature.

This means that at 6 weeks, you do have a 95% chance of ich being totally eraditcated, correct? And it doesn't mean that at 6 weeks 95% of the tomonts are dead, right?

 

[DrBoxedWine]

Also, i know we don't have a standard deviation for Ich, so these numbers inherently can't be counted on precisely.

 

[jbvdhp]

I think he's referring to the crypto itself and all forms of it. I hope he is, cuz I just DT'ed my fish again!

On a side note, sorry OP, I just realized I put ALL my fish in at the same time... I hope I didn't mess up the bio filter! I'm so nervous about fish now.

 

[andy01748]

Hi Everyone,

I have a question regarding Snorvich's post on Ich fallow periods. The info i'm wondering about is this:

These percentages are known as the "empirical rule". What this means for Cryptocaryon irritans is that leaving a tank fallow for 3 weeks will give you a 68% chance that you have eradicated the parasite, leaving a tank fallow for 6 weeks will give you a 95% chance of eradication, but if you want 99.7% chance, you will leave the tank fallow for 9 weeks. That is the reason you see different numbers being used on Reef Central and in the literature.

This means that at 6 weeks, you do have a 95% chance of ich being totally eraditcated, correct? And it doesn't mean that at 6 weeks 95% of the tomonts are dead, right?

I think your last sentence is correct. I read these as statistics for a single cyst, not the odds you have completely eradicated all ich cysts at a particular time. In other words, at 3 weeks, statistically 32% (100-68) of all cysts still remain, at 6 weeks 5% are still viable, and 0.3% at 9 weeks.

 

[DrBoxedWine]

Yeah this is what i'm confused about, as they would imply 2 completely different things. 99.7% of crypto being gone means a few tomonts are still in the tank, and all it's going to take is one getting through, i would imagine.

 

[andy01748]

What makes ich (and other parasites) so nasty is are they are geared for survival in the wide open ocean, where hosts are relatively few and far between. Put them in the confines of a small glass box and .... The expression 'shooting fish in a barrel' comes to mind.

 

[jbvdhp]

I think your last sentence is correct. I read these as statistics for a single cyst, not the odds you have completely eradicated all ich cysts at a particular time. In other words, at 3 weeks, statistically 32% (100-68) of all cysts still remain, at 6 weeks 5% are still viable, and 0.3% at 9 weeks.

AHHH.... smart one, you!!!

 

[DrBoxedWine]

What this means for Cryptocaryon irritans is that leaving a tank fallow for 3 weeks will give you a 68% chance that you have eradicated the parasite, leaving a tank fallow for 6 weeks will give you a 95% chance of eradication, but if you want 99.7% chance, you will leave the tank fallow for 9 weeks.

It seems to me that really reads that at 6 weeks you have a 95% of it being gone (eradicated). But I wonder if this is how it was meant.

 

[Dmorty217]

Being that not all stages of ich will act at the same time... IE. "drop off" all at once and vice versa hence the reasoning behind the longer time than 6 weeks. 5% is still a huge risk that im not willing to chance

 

[DrBoxedWine]

Yeah i hear that. But, 5% chance it is still there is a very different risk than "5% of tomonts are still active". One would seeminly almost guarantee a re-infection, while the other has odds that are quite in your favor (maybe you don't want to take that risk, which i certainly understand as well).

 

[andy01748]

Yeah i hear that. But, 5% chance it is still there is a very different risk than "5% of tomonts are still active". One would seeminly almost guarantee a re-infection, while the other has odds that are quite in your favor (maybe you don't want to take that risk, which i certainly understand as well).

I think "5% of tomonts are still active" is the more correct interpretation.

 

[DrBoxedWine]

Thanks for the thoughts, Andy. It would seem to make the most sense that you're right. But, i mean, when you look at this sentence i feel that the other interpretation is the only way to look at it:

leaving a tank fallow for 6 weeks will give you a 95% chance of eradication

I guess i'm interested in what Snorvich says about this.

 

[Dmorty217]

Thanks for the thoughts, Andy. It would seem to make the most sense that you're right. But, i mean, when you look at this sentence i feel that the other interpretation is the only way to look at it:

leaving a tank fallow for 6 weeks will give you a 95% chance of eradication

I guess i'm interested in what Snorvich says about this.

Either way you look at it Steve recommend 72 days fallow period. He has read many more research papers on the subject than most of us combined. It sounds like your trying to talk yourself into the "6 weeks is enough" thought.

 

[DrBoxedWine]

Nah, i'm about 10 days away from 72 days, i'm definitely not going to cut it short.

I don't imagine anyone saying "OMG, DrBoxedWine just made a breakthrough discovery here and we don't need to QT like we thought we did." I feel like a lot of the fun in this hobby is really getting to understand something, however. I'm also not trying to question or poke holes in anyone's theory. It was just something I noticed the other night while reading about ich.

Steve is incredibly helpful around here and i'm not trying to be annoying. He's given me so much advice (I actually have another questioned i posted for him this morning). But, when i look at that sentence, i can't help but wonder.

 

[snorvich]

Since the longest (currently known) "hatch time" is 72 days (for a given species of cryptocaryon irritans) then the fallow time would be 72 days plus one day for completely eliminating CI from a tank (but I always refer to it as 72 days). The front end of the life cycle (on which tank transfer is based) is very deterministic whereas the back end of the life cycle is highly variable. That is why elimination of cryptocaryon irritans using the front end of the life cycle is preferred as opposed to killing theronts on the back side when emergence from the tomont is so variable. Copper and hyposalinity act only on the theronts (CP acts on theronts and possibly tomonts) which is why copper and hyposalinity engaged for only 30 days sometimes fails to eliminate cryptocaryon irritans.

The sticky found here provides useful information.

 

[DrBoxedWine]

Thanks Steve!