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stuggling with crabs molting


Crys

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The crabs in my tank don't always survive thier molts.  I lost an emerald, anemone porcelian and now my very beautiful blue porcelain.  The blue had gone through 3 molts sucessfully. So I thought things were going good.  The body was emply but the claws still had meat in them and smelled so I know it's dead.  The shrimp and hermits never have a problem.  So I think there is something wrong with my water. I haven't tested for iodine or strontium.  I really find crabs interesting but don't want to condem anymore to their deaths.

 

Tank 13.5 gal   1.5 years old

Alk 7.5  

Mag 1350

Cal 350

phosphate  .075  (I have lots of macro algae that keeps the numbers low)

Salinity 1.25

 

Stock

2 clowns

watchman blenny

tail spot gobby

20 snails

2 blue hermits

emerald crab (hasn't molted yet)

pepermint shrimp

tiny sea urchin  (can trade in with LFS as it grows)

 

Thanks

 

blue crab.jpg 2.jpg

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Best guess is your calcium level. Molting is calcium dependent.

 

When it comes to crab molting issues and specifically incomplete molts, calcium and iodine would be the first thing I look at and your calcium is quite low - even for a low alkalinity tank. Is there a specific reason your calcium is that low? Even at your alkalinity, I'd still be aiming for a minimum of 400ppm.

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I am not sure why it is that low.  I desided that the alkalinity is stable so I wouldn't change it, but I didn't realise it tied to calcium.  I use RO water, but I live in the country so the water still comes from my tap, and goes throught system.  Could it be that there isn't much from the local source?

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6 minutes ago, Crys said:

I am not sure why it is that low.  I desided that the alkalinity is stable so I wouldn't change it, but I didn't realise it tied to calcium.  I use RO water, but I live in the country so the water still comes from my tap, and goes throught system.  Could it be that there isn't much from the local source?

No - your calcium level is determined by your salt mix plus anything that you are dosing to increase/replenish it. What salt mix are you using and are you dosing anything? How often do you do water changes? And how heavily stocked with stony corals is your tank?

 

You are going to use somewhere between 6.4 and 7.1 ppm of calcium for every dkh of alkalinity used up. If you have fairly high alkalinity salt mix and your water changes changes aren't keeping up with your usage, that would be a good candidate for how your calcium is so low with a fairly-low, but still in normal range, alkalinity. That or you just have a bad salt mix or are incorrectly dosing your tank.

 

You definitely need to bring that calcium up. Whether that means doing more water changes, switching salt, or dosing is entirely dependent on what your goals here are and where your tank is at now.

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Hi,

 

I use aquavitro, salinty for reefs. I was told it was a very good brand. I do a 10 % change every weekand a half. Maybe I need to go to every week.  I only have 2  small stoney corals, the rest are zoa's and muchrooms.  I do have dragons breath and mermaid fan macro algae.

 

 

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Your salt mixes 400-440 ppm of calcium and 9-10 ish dkh. Something is using that up (maybe coralline, maybe your gfo is causing issues). Test your fresh water to make sure it's in range and not a bad batch.

 

You should probably do some larger water changes, stop the GFO, and monitor both alk and ca.

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Thanks,

 

I will do that and see what levels I get after.  I do have a lot of coralline. I have to scrape it off the glass everyweek. Rocks, snails and poewer head are covered.

 

Appreciate your help!!

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I have one more question.  I can't get the usual salt I buy, lots of things are out of stocke, is the red sea coral pro salt the same quality?

 

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11 minutes ago, Crys said:

I have one more question.  I can't get the usual salt I buy, lots of things are out of stocke, is the red sea coral pro salt the same quality?

 

Yeah it's good. Alkalinity is well over 11 dkh, so be really careful. It would be better if you are on limited stock to just go with original instant ocean. But really any if fine, just slowly switch over with lots of small water changes.

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