From petshrimp.com

[Veneer]

I just came from reading a post in petshrimp.com where the moderator 'Mustafa' argues adding iodide is not necessary since it is not found in freshwater. Someone points out that if iodide is not necessary, why is it an ingredient in most shrimp foods? Then he goes on to say, if it has any benefits for aiding molting, its best ingested anyway, and not simply added to the water.

Actually, the exact statement was:

I found calcium iodate in certain brand of fish food and kelp (rich in iodine)is used as the main ingredient in a couple of brands for freshwater shrimp food.

It won't make sense to use them as ingredient if they are not useful for shrimps.

By "IKnowShrimp" (from http://www.petshrimp.com/discussions/viewtopic.php?t=620&start=0).

I am inclined to believe that calcium iodate content is more of an incidental result of ingredient composition than a purposeful attempt to deliver the chemical. [I am not, incidentally, aware of any brands of food specifically marketed for freshwater shimp. As for the second statement, fish foods do contain a certain quantity of "filler".]

The primary objection to iodide dosing for freshwater shrimp is that there is, as I have stated before, absolutely no empirical evidence that shrimp are even capable of metabolizing such supplemental products from the water column.

I do not deny that iodide is necessary, in trace quantities (easily obtained via foodstuffs, if the figures for Penaeus chinensis shown below are of any significance), for freshwater shrimp.

A condensed "reading list":

Chemistry and the Aquarium (one section is specifically devoted to shrimp):

Who uses iodine: Shrimp

As one moves up the food chain to more sophisticated organisms, data on their ability to take up iodine from the water column becomes very sparse. Shrimp are known to have a need for iodine to grow, but that is only known in terms of a dietary requirement. The shrimp, Penaeus chinensis O'sbeck, for example, grows optimally when the diet contains 0.003% iodine.56

Shrimp apparently incorporate substantial amounts of iodoorganics into their bodies. The shrimp Pandalus borealis, for example, incorporates between 0.04 and 2 ppm iodine as iodoorganic compounds depending on the particular body tissues examined. Their roe were somewhat higher, up to 4 ppm iodine as iodoorganic compounds.57 Shrimp shells and other parts can contain up to 17 ppm by dry weight iodine, the majority of which is iodoorganic compounds58, but the values are still far lower than for other inverts like macroalgae, sponges, or gorgonia.

Still, the amount contained says nothing about whether iodine is an important requirement. I could find no scientific studies that showed that shrimp need iodine from the water column, but neither could I find any that demonstrates that they do not.

A discussion (if only anecdotal - and thus no less or more trustworthy than allegations to the contrary) of [marine] iodine supplementations, with some intriguing commentary concerning crustacean molting:

(An excerpt):

Ron Shimek wrote in last months FAMA that Iodide is poison and is dangerous to use. He stated there is not scientific proof that Iodide is even used by corals and that hobbiest [sic] test kits and [sic] not accurate and you can not [sic] maintain levels equivalant to the sea by use of these kits.

Investigating the Composition of the Exoskeleton of Macrobrachium rosenbergii - an inquiry into the particulars of this freshwater prawn's molting cycle.

Chitin
.
.
Chitin synthesis in shrimp cannot be considered out of the molting cycle, which shows the evolution of organic reserves in the digestion gland. Renaud (1949) clearly demonstrated in crabs the variation in glycogen. Also Cuzon (1976) reported this in M. japonicus, and again glycogen in hypodermis, which
indicates an intense metabolic activity including important transport of nutrients from an organ to another, starting in stage C of the intermolt period and in preparation to the next molt. Such transfer [sic] imply hemolymph which dispatch nutrients to different tissues in which metabolism will be oriented according to a given period of the molt cycle.

(From http://www.uanl.mx/publicaciones/maricultura/acuiculturaV/gcuzon.pdf)


The potential endocrinological effect of iodine metabolization is, to my knowledge, an uninvestigated branch of inquiry (see http://ss.jircas.affrc.go.jp/kanko/seika/seikah8/4-13.html).


Continuing along this track of thought, "liquid iodine" supplements' alleged effects on shrimp molting (if, in fact, valid) may come through interference with "molting" and "molt-inhibiting" hormones:

In M. rosenbergii and most other species of decapod crustacea including crabs and lobsters, the physiological processes of molting and reproduction are inextricably linked and under the control of various hormones. Crustaceans, which are arthropods, bear much endocrinological similarity to insects, and differ greatly from vertebrate species. However, compared with insects, which have been studied more widely, little is known about endocrinological mechanisms in Crustacea.

It is well-established that ecdysteroids such as 20-hydroxyecdysone serve as “molting hormone* in Crustacea and are excreted from a tissue known as the Y-organ. On the other hand, peptides (molt-inhibiting hormone: MIH) originating in the sinus gland complex of the eyestalks exert negative influence on molting. In M. rosenbergii, molting occurs approximately once per month accompanied by growth of the animal. In females, reproduction occurs in synchronization with the molt cycle during which vitellogenin (yolk protein) is produced and ovaries develop and mature. This process is also under the inhibition of an eyestalk hormone: vitellogenesis-inhibiting hormone (VIH). In hatcheries and on prawn farms, the technique of eyestalk ablation has long been employed to induce female maturation; the basis of this is the removal of the eyestalks and thus the removal of the source of these inhibitory hormones.

(From Molting and reproduction in the giant freshwater prawn, Macrobrachium rosenbergii: Endocrinology and potential aquaculture applications)

(My emphasis throughout)

 

[RTR]

The absolute quantity of iodide in iodized salt is so small as to be trivial. I would not count on it to do the job, but without better info on how much is needed, we are really groping in the dark.

It may also be a function of how much is in the soil and groundwater. Many areas of the US have soils severely deficient in iodide. That is why iodized salt is standard in this country. We were once in large part a localized farming based economy, deficiency was common in wide areas. These days that is far less likely as our food supply has not been localized in a long time. Our fish food is even less so.

 

[Swimfins]

Who uses iodine: Shrimp

As one moves up the food chain to more sophisticated organisms, data on their ability to take up iodine from the water column becomes very sparse. Shrimp are known to have a need for iodine to grow, but that is only known in terms of a dietary requirement


Thanks Veneer, I read most of that article but gave up after awhile.
That part about 'Iodine' threw me.

I will dose some 'iodide' as RTR does, I was just curious about the table salt.

 

[Blinky]

SF, I use iodide (Kent Tech.I) at 1/2 dosage at each water change, and the reason is not at all scientific. RTR uses it, it works for him, and I've seen several successful molts since using it - that's good enough for me .
I feed my little guys lots of different foods - crab cuisine (made by Hikari - says it's a scientific diet for crustaceans, it's high in Ca which is important, since my water is very low in Ca), crushed freeze-dried shrimp, krill, staple flakes, veggie flakes, daphnia - I try to make sure they get a well-rounded diet, just like the fish. I find it helpful to have lots of snails in the tank with them, since I crush everything up fine so they can filter it out with their fans and I'm sure they don't get it all. As a bonus, the crab cuisine seems to be giving the ramshorns the extra calcium they need to grow strong, beautiful shells

 

[Veneer]

Who uses iodine: Shrimp

When aquarists colloquially refer to supplemental 'iodine' or the like, they may have any of several disparate elements/compounds in mind.

 

[Swimfins]

Thanks Bkinky, I'll pick up some crab cuisine and the Kent iodide tomorrow.

Veneer: You obviously are scientific in the field. I apologize, I'm just a layman who happened upon some of these shrimp. By rights, I should not have bought without looking up information first. But, once I lost out on some beautiful German Rams, because I thought they'd still be there when I was ready. (But, of course when I decided to buy, they were all gone).

I'll keep on reading your links as time goes by some might just sink in.