Hermit Crab Salt Products

[Wai]

Introduction
Hermit crabs need sea salt in their diet as well as for moulting. The choice of sea salt products for hermit crabs has been discussed in several other threads; however, some of the arguments that I have read against the use of salts targeted for hermit crabs don't make sense to me. As I am not sure which members have a scientific background, I will do my best to explain some basic concepts first.

What is salt?
Salts are not elements, but molecules that consist of a metal (e.g. sodium, potassium) and a halide (e.g. chlorine, iodine). When exposed to water, the salt readily dissolves into the ionic forms of the metal and the halide (ion = charged atom). For example, when a sodium chloride (NaCl) molecule dissolves in water, it splits into a sodium ion (Na⁺) and a chloride ion (Cl^-). Do not confuse sodium metal (Na) and chlorine gas (Cl₂) with their ionic forms. Pure sodium metal reacts violently with water, while chlorine gas may cause blisters in the gills of hermit crabs. On the other hand, the ionic forms of these two elements are very stable and are not health hazards to hermit crabs. Likewise, when two potassium iodide (KI) molecules dissolve in water, it splits into two potassium ions (K⁺) and two iodide ions (I^-), not pure potassium metal (K) and pure iodine (I₂).

What is in sea salt?
Sea salt consists of many different salts. Once these salts dissolve in water, they all split into the ionic forms of the elements. When the water is removed, the ions will recrystallise back to their solid salt forms; however, the ions may "swap" partners during the recrystallisation process. For instance, if you dissolve a molecule of sodium chloride and a molecule of potassium iodide in water, then heat the mixture to evaporate away the water, you might still get sodium chloride and potassium iodide, or sodium iodide and potassium chloride. The major component of sea salt is sodium chloride. Generally, it does not matter which metal pairs with which halide, since they will all split into ions when dissolved in water. A list of the ions formed from dissolved sea salt can be found here (I wish I could find a more academic source instead).

What is in table salt?
Table salt is pure sodium chloride; however, anti-caking agents are often mixed in with the sodium chloride. These anti-caking agents are believed to be toxic to hermit crabs, which is why table salt should be avoided. I often hear people arguing on this forum that table salt is toxic to hermit crabs, because it "contains sodium chloride". This is not true. Sodium chloride, sodium ions and chloride ions are harmless to hermit crabs. As I mentioned earlier, do not be alarmed by the word "chloride" as it sounds like "chlorine". Elements in their uncharged pure form have very different chemical properties to their ionic forms. Chlorine gas is toxic, but chloride ions are not. When hermit crabs drink salt water, the sodium and chloride ions remain in their harmless ionic forms throughout their body.

Is iodine deadly to hermit crabs?
Again, do not confuse solid iodine (I₂) with the iodide ion (I^-). I think iodine is deadly to hermit crabs (as it is to people), but iodide ions are safe in low concentrations. Hermit crabs need iodide ions in their diet for metabolism. I will update this paragraph as I find out more information about iodine and its ionic form.

Should I use table salt?
If the table salt consists only of sodium chloride, then it is safe for hermit crabs. However, sea salt will dissolve to form a much wider variety of ions in water, all which are needed in a hermit crab's diet. Also, manufacturers may leave out anti-caking agents in the ingredients list of their table salt; therefore sea salt is the superior choice.

How do dechlorinators work?
Dechlorinators consist of electron-donating agents that convert any dissolved chlorine gas and chloramine into harmless ions such as chloride.

Why do heavy metals in tap water need to be removed?
Many heavy metals are soluble in water. Some of these heavy metals are harmful to hermit crabs.

Discussion
Now that I have cleared some things up, I have some questions for everyone else too, regarding this article.

HBH Hermit crab sea salt Ingredients: sodium chloride, magnesium chloride, calcium chloride, potassium chloride, potassium iodide
It contains the wrong form of calcium and it contains normal table salt ingredients sodium chloride/ potassium iodide. HBH salt mix also contains a highly corrosive magnesium chloride that is used to stabilize the iodine. (Thanks to SUE, RFCrabs for this information regarding HBH salt mix)

On the bottle of HBH Hermit Crab Salt, it says that it contains only "salt" and "calcium carbonate". Where did you get the expanded list of salts?

What do you mean by the "wrong" form of calcium? Calcium chloride is very soluble in water and will dissolve into calcium ions (Ca²⁺) and chloride ions, both which are harmless to hermit crabs. Sodium chloride, potassium chloride and potassium iodide are all components of sea salt.

What do you mean by magnesium chloride "stabilising" the iodine? Magnesium chloride is also a component of sea salt and splits into harmless magnesium ions (Mg²⁺) and chloride ions in water. No iodine is formed when HBH Hermit Crab Salt mix is dissolved in water; however, you could argue that iodide ions are deadly in high concentrations.

ZooMed Part 2 has a yellow dye within it, something a hermit crab does not need within their diet. Within this product, it does not contain an ingredient to remove heavy metals from tap water, as well as ZooMed Part 1 fresh water conditioner does not contain a heavy metal neutralizer.

I am fine with this one, as dechlorinators must be able to remove harmful heavy metals in water.

If one mixes the ZooMed part 2 (as well as the hbh hermie salt) neither one register on a hydrometer.

The specific gravity of water will always increase when salt is added. Sorry to say this, but I am a bit doubtful that the ions in the water can just disappear overnight. Unless it isn't salt at all, it doesn't seem possible. Specific gravity decreases as temperature increases.

"In one gram of sodium chloride, there are approximately 0.3933 grams of sodium, and 0.6067 grams of chlorine."

And we know the results of what chlorine will do to hermies.

Sorry to edit this in, but I just want to remind everyone that harmless chloride ions are formed when salt dissolves, not toxic chlorine gas. Also, if crystals of sodium chloride were deadly to hermit crabs, then we could kill our hermit crabs by throwing sea salt at them, which obviously isn't true.

Conclusion
I'm not trying to jump on Marie here. I really appreciate her contributions to this forum; however, I want to have this issue with sea salt rectified, because a lot of the arguments I have read do not seem to make sense to me. Ultimately, salts targeted for hermit crabs should still be avoided. Even if they are harmless to hermit crabs, they are still missing many elements in sea salt that hermit crabs need in their diet.

[ladybug15057]

Well I had never claimed to be a scientist and not sure of any experienced crabbers, or even moderators/owners who have claimed to be so our scientific 'language' maybe off.
As for the posting from the CSJ archives from Sue regarding HBH salts, this is something that should be directed to her. (possibly on CSJ)
But as you also noted, there are times too that manufacturers do not list all the ingredients on their products. HBH had been approached regarding their product and within a VERY short time the label changed.
As for ZooMed Part 2 having yellow dye within it, it was not Sue who had wrote that, it was me who found it on the label of the ZooMed Part 2 box as well as it not noting that it removes heavy metals from tap water. (as well as on a couple sites it is sold on)

The specific gravity of water will always increase when salt is added. Sorry to say this, but I am a bit doubtful that the ions in the water can just disappear overnight.

True, and the crabber had tested the salts geared towards hermies when they mixed them. They also tested them the next day. Neither one was she able to get a reading from when she tested them.

Wai, you're questioning a bit from the CSJ information that is within articles and other areas as well. Why not post this there too? A lot of research and experience is behind the information that is there. This information still undergoes research too as time goes on.

[Wai]

That's okay, Marie. I don't blame anyone. I am aware that a lot of research was done in writing up the CSJ article, but I couldn't resist correcting some of the very basic concepts regarding the ionisation of salts in water. To be honest, I feel that the world needs a land hermit crab scientist, not another pharmacist, but I have learnt a lot of useful information from my course which can also be applied to hermit crab care.

By no means am I trying to convince anyone to use table salt. Rather than arguing whether table salt is toxic or not, we should be arguing that table salt lacks many of the essential elements that sea salt is made up of.

[emmac350]

I've always assumed that the problem with table salt is that in order to reach the same level of 'saltiness' (sorry, I'm tired and can't think of the proper word to use there - maybe the same concentration of dissolved ions?) you would have a much higher concentration of the sodium and chloride ions and that can be irritating to crabs? There are, like you described, many other ions found in ocean water than just sodium and chloride, so perhaps the combination of the various ions and the lowered concentration of the sodium and chloride ones lowers the effect of the sodium and chloride on the crabs?

I was a computer person in college, so I didn't spend too much time paying attention in chemistry (just enough to get an A and move on ) but it's just a thought.

[Wai]

Table salt will yield a higher concentration of sodium and chloride ions, but hermit crabs can dilute the water using fresh water, so that shouldn't be a problem at all.

[ladybug15057]

Edit by Wai: Added link, sorry.

To get more involved if certain information is being taken from the CrabbyWiki or the Crab Street Journal (articles, FAQ's caresheets, etc. or the archive entries to CrabbyWiki) and it is being assumed I 'created' it due to in the upper right or lower section of these entries it states "Ladybug15057" please be advised, when the CSJ changed hosts I helped move the information from our old host to the CSJ new host and CrabbyWiki. This does not mean I am the true author of the information and should be approached on the Crab Street Journal.

[emmac350]

I had an idea about this this evening as I was discussing crabs with a friend of mine who just got some and had me over to get advice/how to information.

Could it be that the main ions crabs need from their salt water isn't the sodium and chloride ions? Maybe some of the less common ones in the ocean water are the ones they are truly after? Because (I know I talk about this a lot, but it's my best example) my two adoptees were for a year only given the 'salt water conditioner' by ZooMed, and they rarely (from my understanding from their owner based off of emails and talking with her about them) even touched it. When I gave them my Oceanic mix, they came running like I'd just offered them the most amazing thing ever. Maybe they didn't realize that the ZooMed stuff was salt water because it didn't match their expectations with what it was supposed to be?

[ladybug15057]

Could it possibly be too that the hermies did not even recognize the ZooMed part 2 as even being an ocean water source?

A recent thread on Crab Street Journal:

http://crabstreetjournal.com/xoops/modu ... mpost17394

Now at the end of the Ocean Mix article on CSJ I had added what a biologist (a member of CSJ) had sent me via private e-mail regarding fresh water mixes too. A few years ago I did get into a 'discussion' about there being a difference between fresh salt water and ocean salt water. And there IS even in the natural fresh and ocean water mixes. (found on the internet)
For the record too, quite a bit of the information on Crab Street Journal was acquired from crustacean scientists/biologist journals and even a few e-mails had been exchanged.

[Wai]

Sodium, potassium, calcium and chloride ions are all involved in the formation of cellular action potentials for muscle contraction (i.e. movement).
Source: Vander's Human Physiology, 11th edition.

I'm pretty sure that sodium and chloride ions are needed in their diet. Although I referenced that from a textbook for human physiology, there aren't any animals that I know of that don't need to rely on those four ions for muscle contraction; hence, sodium chloride is not deadly to hermit crabs.

Does the ZooMed stuff come in a liquid, or as salt crystals like most other products?

Marie, I hope you don't feel that I'm attacking you. I am aware that you aren't a scientist. I could post this at CSJ, but I would prefer keeping the discussion here instead. After all, no-one has replied to that debating topic at CSJ for a year.

[emmac350]

The Zoomed part 2 stuff is a yellow liquid ("yellow dye added" so you can tell the water bowls apart) that you're supposed to add 3 drops of (if I remember right) to a bowl of water.