15G - heating question

[RoxyDog]

congrats, you've experienced your first molt.  well not YOUR molt...but your crab's.  he's likely hiding away pointing and laughing from his spot, as I'm sure mine did when I saw it for the first time and thought my crab died.     seriously, it's most likely a molt.  your salinity, I'm curious as to why it's so low?  not more like 1.025-1.026?

[kennyman]

Specific gravity is temperature based Roxy. 1.023 is not low at 76 deg. 

As the temperature increases the SG reading needs to change to keep the same ppt

[KLKelly]

Ok - he's laughing and maybe I will be soon. I never thought of that because it looked so whole. For some reason I thought the shell would be less colourful or I would be able to tell it was a molt. Geesh!

I'm confused about the SG as what I've read stated to keep it between 1.021 and 1.024 not to go above or below this.  If we did a water change and it went above 1.024 that we should remove some of the water and add fresh water back in to get it lowered.

[sdivell]

in a 15g tank its better for you to keep the salinity on the lower end... .023 is good.. as your water evaporates the salinity will increase.  so if you keep your salinity low as it rises it'll stay within range.

and yes its probably just a molt. A sign that your crabs are very happy in their new home.

[Vallely4]

Actually it could be a dead crab, as you did discribe he hasnt a full body like you seen before.
In my tank, ive never yet seen a molt , but i've seen a few crab carcasses.
I've lost 3 crab, and i KNOW they weren't a molt as I havent seen them since. The other crab tend to do a pretty good job of cleaning up, leaving only legs behind...
They seem happy and active enough

My ammonia or nitrate's didnt skyrocket or anything, the crabs just had a quick meal- but just letting you know that I belive (and was told) its common to lose a couple hermits

Does anyone know whether crabs need somthing special to molt?
And I think your correct -remove -add top up water to balance the tank out to the right SG, around 1.023 is perfect I was told by my LFS

[RoxyDog]

Specific gravity is temperature based Roxy. 1.023 is not low at 76 deg. 

As the temperature increases the SG reading needs to rise to keep the same ppt

Sorry Karrie for the threadjack...but you said you were confused too.   I forgot about the temperature affecting it.  my tank sits @ 1.025-1.026 but it's 79-80 degrees.  it was my understanding @ that temp, it's the right sg.  mine gets slightly higher than that between top ups but nothing has every seemed to care.  is mine too high then...and if Karrie's went down to 1.021, wouldn't that be WAY too low?     I shall google and hope to find some answers. 

I thought molts were legs (or mostly legs) only...

[KLKelly]

I am going to look also - I wasn't up to speed on the temperature component to salinity 

[az]

most likely it is still inside the shell hiding, thx.

[KLKelly]

I found this on a nano-reef article:

When your specific gravity (salt level) is at 1.023 at a temperature of 80F the water should be ready to add to your tank. One thing to remember when testing your specific gravity with a swing needle hydrometer (the most commonly used) is that they're only calibrated to give a good reading when the water temperature is around 80F. If it is colder, your specific gravity will seem low. Some more accurate choices for test specific gravity are refractometers or floating hydrometers. When those levels are good, the only other thing you should test for is the pH. It should be at 8.3 before you use the water. If it is too low you may need to add a pH buffer.

The effect of temperature from this link seems extremely minor: http://www.algone.com/salinity.php

I'll have to figure out a way to get the tank to 1.023- I top off the water every night.

I will up the temp to 78. It goes up to 77.5 when the lights are on so 78 will be more consistent.

We just picked up RO water - I haven't checked the PH but I assume its 7.0.  What product do you guys use to bring up ph in the bucket before using it for water changes?

[Cheebs]

I thought I had mentioned it, but I guess I forgot to hit post .  Anyways, about the dead crabs, I experienced the same thing, after a few days in the tank, all sorts of "dead" crabs started popping up every couple days.  I could never figure out why and could never find the empty shells.  It was their molt of course.

[Vallely4]

 "I thought molts were legs (or mostly legs) only..."

I'd like to see a definitive pic of a molt...
I have never seen a molt in my tank- and Ican swear by that because I know where there old shells are... The legs on the substrate in my tank are definately left overs from what my hermits pick off the dead carcass

[RoxyDog]

We just picked up RO water - I haven't checked the PH but I assume its 7.0.  What product do you guys use to bring up ph in the bucket before using it for water changes?

nothing, I just add the salt and adjust the temp if it's way off.  not sure what would happen if you did some HUGE water change, but small water changes without a ph adjustment don't seem to hurt anything.

I'm not saying for sure it's a molt, I'm just going with "most likely".  but any legs I've encountered didn't end up being a missing crab, they were a molt which may or may not have including upgrading shells.    *shrug*

[KLKelly]

I think it was a dead crab but I hope to be pleasantly surprised - guess we'll find out withing a week or two.  It had a string of fleshy stuff attached.  I just wanted to ensure it wasn't the water or anything else.  There are extra shells in there now.  Nitrites are also 0.

[KLKelly]

Good to know about the water!  Thanks - makes things easier.  We are doing small top ups each day - guess it helps that we don't have the MH lighting or hot T5s 

[Funkmotor]

I have a scarlet that's moulted twice since I got him/her about 6 weeks ago.  They have both been complete shells...every part of the crab is there, and it's like a trapdoor was opened in the back.  There was some yellow/white fleshy stuff attached to one of them as well.  Due to the light weight, it's difficult to tell if anyone's home until you see them hiding out back in the tank.

To try to clear up some of the misinformation here, crabs have an exoskeleton.  That means they have no bones and their outer shell is the only thing that gives them any rigidity at all.  They will moult their shell at intervals based on their growth rate, cycle of the moon and other factors.  (I know for sure that Lobsters moult based on the lunar cycle.)

Once they wiggle out of their existing hard shell, a new (and soft) inner one is exposed.  The crab then expands this new shell to full size and then waits for it to harden.  Things like calcium concentration in the water affect the time required for this to happen, and also if it will happen at all.  (If your calcium level is low, there may not be enough to harden their new shell.)

The only reason you will ever see an incomplete moult is when the crab itself or something else eats part of it, or if it came off in pieces.  By the very nature of an exoskeleton, the entire outer surface of the animal is shed in a moult.  All of it, every time.

Crabs and other arthropods can also get themselves in trouble during a moult.  They can get limbs stuck inside the old shell and have to pull them off to get free, and Mantis Shrimp have been known to perish while moulting - I would imagine that's a pretty complex operation anyway.

You can tell when your crab is getting ready to moult when their colour starts to go milky.  This tells you that the outer shell is starting to detach from the new one growing on the inside.

Personally, I love how bright the red is on a Scarlet after they moult.

[KLKelly]

More questions for you guys.

These things just seemed to appear overnight.  We have had the lights turned off in the tank for a couple of days to help with a lot of algae (my fault I left the lights on during the rock curing stage).  They are like lime green growths on the rock that stick out.  Any ideas what these green things are?



Trying to get the picture edited to show a closer look:


Also - we found something not alive in the fuge.  We were getting ready to add some of our smaller pieces of our live rock to the back of the empty fuge (just cheato in there now).  I've seen pictures of this and from what I remember reading they are harmless.  I can't remember the name.  What is it called?




The tank only has snails and scarlett hermits.  There are a number of types of algae growing including a new type from the last couple of days that I've seen also.

1. A dark gross coloured sticky/stringy algae - similar to hair algae in freshwater the way it sticks together.  Is this hair algae in sw?
2. Bryopsis.  Ha - I thought the first strand was pretty - now its growing in a lot more places.
3. I think it is an algae.  Its a single almost lime green coloured bubble.  If this is bubble algae - how can I pick them out so they don't get like the bryopsis.

Thanks guys!!!!

[mdugly]

Any ideas what these green things are?

Looks like Neomeris annulata
See http://melevsreef.com/id/algae.html

The other looks like an amphipod.

Both are good 

[KLKelly]

Thats a cool site - thanks!!! The green bubble thing we have looks just like a single one of picture of Caulerpa racemosa.

Thanks!!!!

[artw]

Looks great Karrie. 

[Cheebs]

The hairy stuff is most likely hair algae.. I had a bit but it's all gone now.  As for the Bryopsis,  I've got some growing too.  You can manually remove it, but some fish will eat it I believe.  It seems if you keep good water conditions in the tank it won't spread too much,  and I think it looks kind of cool hehe,  at first I thought it looked alot like Chaeto.