Hyposalinity and Ich

[MILPIL]

Here is where you can get a gist of the Aquarium Systems Article
http://www.aquarium-design.com/fish/lowsalinity.html

 

[Stark]

There's alot of (mis)information out there; sifting through it is the tricky part.

 

[Anonymous]

I thought that in order to "get" the ick by hyposalinity, you had to change the specific gravity quickly as in a freshwater dip. The parasite can't osmoregulate fast enough and his poor little body justs busts open. ???

Glenn

 

[Terry B]

Randy,
While I appreciate your intentions I also think it is necessary to continue to mention both specific gravity and salinity. If both are not mentioned too many people assume that both terms mean the same thing. Mentioning both helps point out the fact (as I did) that there is a difference between specific gravity and salinity. I can’t spoon feed everyone. I simply don’t believe withholding information (i.e. specific gravity) is in the best interest of educating hobbyists. BTW, I am perfectly comfortable recommending hyposalinity therapy between 14 and 16ppt. Personally I prefer to treat at 14ppt. The internal salinity of marine fish is about 11ppt. This of course can vary a bit with the species and size of the fish. I emphasis keeping the surrounding ambient water at a slightly higher salinity than the internal salinity of the fish being treated. As long as the external salinity exceeds the internal salinity of the fish they can continue to osmoregulate in a normal (although less costly metabolically) manner.

Starks,
I think that the crux of the matter is that specific gravity is influenced by water temperature making it a less reliable (or accurate) means of measurement. I fully agree with this fact. This is in part why I generally mention both parameters. Randy believes that I should withhold mentioning specific gravity at all. However, I prefer to use both means of measurement.

MILPIL,
I don’t know who wrote that article, but I can tell you that it is not accurate. As a matter of fact, two and a half years ago Tom Frakes and I had lunch in Vancouver Canada while attending the Western Marine Conference. We talked about hyposalinity and how to use it. If you want to see what they actually use then it is easy enough to check for yourself. Simply check the Seascope article (Tom is the editor) that describes the procedure that they use.
It was first mentioned in the Volume 11, Summer 1994 issue of Seascope. Seascope published a more detailed article about hyposalinity in a later issue (it may have been the spring 1998 issue).

Rover,
Hyposalinity does not kill Cryptocaryon irritans because they cannot osmoregulate. It kills them by interrupting the tomonts ability to excyst (hatch). This effectively stops reproduction.
Terry B

 

[randy holmes-farley]

OK, let me be more specific. I too would never withhold information. But that information needs to be correct and unambiguous. Terry is reporting sg as many hobbyists do, in a way that is ambiguous at best and simply wrong at worst.

To say

" This translates to a specific gravity of about 1.009 at 78 to 80F. "

is incorrect, or at least ambiguous enough that many reefers will use the wrong interpretation.

There are two reasons for this ambiguity. The main one of those is that different hydrometers are calibrated for different temperatures. Many reefers (myself included) have hydrometers calibrated to be used at 77 deg F, but that's clearly not what Terry is using. If I used that hydrometer to follow his advice, I'd end up using 11.7 ppt salt water, and not 16 ppt. People in this hobby have conveniently ignored this issue for long enough that it is entrenched in the hobby literature to the detriment of those trying to understand what people really are talking about.

FWIW, any mention of sg determined with a hydrometer really needs to report ALL of the following:

1. The standard temperature being used. That is, the temperature of pure water that the sample is being compared to.

2. The reference temperature. That is, the temperature that the hydrometer is intended to be used at.

3. The sample temperature when the measurement is made.

That's why all quality lab hydrometers have both the standard temperature and the reference temperature on them. It is usually reported something like "Temperature Standard 60 deg F/60 deg F.

FWIW, Stephen Spotte has a nice discussion of such issues in "Captive Seawater Fishes".

So how should Terry report sg in such a context? Here's my suggestion:

"This translates to a hydrometer reading of about 1.009 at 78 to 80F using a 60 deg F/60 deg F hydrometer."

 

[suckair]

The one way to quickly remove ich from a system is to remove the stress! I have picked up infested fish and with in a a week they are cured while at the same time the other fish don't get it!

Randall

 

[Terry B]

Randy,
Point well taken. I will keep it in mind. I have been looking for a good salinity to specific gravity conversion table online. One with a calculator would be nice. Do you know of one? BTW, I think most of the hydrometers sold in pet stores are now calibrated for reef type temperatures. Also, people tend to read hydrometers incorrectly at the top of the meniscus instead of at the water level. This can give people a false low reading.
Terry B