HCA: Hermit Crab Association

So I've got a standard 40b that's 36x19x19 and I have one small a little bigger than a quarter and two what I'm going to call larges as they're just a tiny bit larger than a golf ball I would say. And another large that's bigger than them but not quite tennisball size, waiting on him to come up from destress/molt in the tank they were in prior to upgrade, waiting to see if he makes it or succumbs to PPS but things are looking good so far. So 1 small and 3 large total. My tank has 6+inches of sub and a huge open second level that spans 36x10ish. Am I just about at capacity or do I have room to rescue a couple in the future if I need too? Thanks in advance for your help

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I would say you are at capacity or slightly over capacity already. I have 5 crabs in my 75g and it's crowded!

http://hermitcrabassociation.com/phpBB/ ... 51#p836451

according to JMTs crabs per tank guidelines you can fit 5 large crabs alone in a 40 gal. so based off of this you are not over capacity. if it were my tank tho i would leave it as is in case i needed to rescue smaller crab or something.

They seem to be happy and everyone has their own hide, so I suppose I could leave the tank as is unless I run across a couple smalls that really need a better home

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I have 5 PP's in a 40 gallon and it's quite spacious, I'd say it really depends on the setup more so than the capacity because if you have a multi-layer 30 gallon vs a 40 with 1 level then really all that extra capacity is lost and unreachable. Nonetheless my crabs seem to enjoy their setup and they tend to sleep together making the space even greater, I hope to one day have 8 in there and expand the top area a bit to compensate.

In most pet pamplets it says two crabs per 5 gallons that is so wrong! DONT TAKE ANY ADVICE FROM PAMPLETS. They are eeeeevil...... I say about 2 medium crabs per ten gallon. good luck!

\CLAWZILLA/ wrote: ↑

Thu Jul 08, 2021 8:38 am

I have 5 PP's in a 40 gallon and it's quite spacious, I'd say it really depends on the setup more so than the capacity because if you have a multi-layer 30 gallon vs a 40 with 1 level then really all that extra capacity is lost and unreachable. Nonetheless my crabs seem to enjoy their setup and they tend to sleep together making the space even greater, I hope to one day have 8 in there and expand the top area a bit to compensate.

The limitation is molting space, really. When using the above guide for number of crabs per what size tank, it takes into account how much space is needed for them to tunnel and molt and not come across each other. It's 'floor space' vs total space. A 30 gallon with multiple levels and toppers is still a 30 gallon for molting space.

I know it is tempting to "collect 'em all," and it hurts our hearts to see crabs in need, but in fact adding any crabs to an established group greatly increases the probabilities of aggression, injuries, and molting cannibalism. It is also really important to consider how many softball-sized crabs you are really going to want to be taking care of, 20 years from now. Take a peek at what it would cost you just to buy enough shells to have three each for 5 jumbos, and you might decide that 5 is quite enough.

DragonsFly wrote: ↑

Thu Jul 08, 2021 11:27 am

I know it is tempting to "collect 'em all," and it hurts our hearts to see crabs in need, but in fact adding any crabs to an established group greatly increases the probabilities of aggression, injuries, and molting cannibalism. It is also really important to consider how many softball-sized crabs you are really going to want to be taking care of, 20 years from now. Take a peek at what it would cost you just to buy enough shells to have three each for 5 jumbos, and you might decide that 5 is quite enough.

OMG the cost of Jumbo shells!! It is the biggest expense in all my years of having my crabs!

Each Jumbo shell can cost as much (and sometimes more) as a ten-gallon tank! Eeek!

Good Solid Jumbo Shell: $15.99
https://www.amazon.com/dp/B08G572DDV/re ... UTF8&psc=1

Solid ten-gallon tank (not to say that jumbos should be kept in 10g!): $14.72
https://www.walmart.com/ip/AquaCulture- ... /144433503


Geesh! Jumbo shells are expensive!

Yes, and you need three per crab, at least. If they don't like the ones you buy at first, you may need more.

Plus, a tank big enough for 12 to 18 inches of substrate, bigger water sources, more food, etc., etc., etc. And then there's the fun of waiting 2 years to see if your biggest guy is going to come up from his latest molt, while continuing to maintain conditions and keep fresh water and food sources in there, just in case. . . . .

I have paid $25 each for jumbo shells....and I am by the beach.

How did you construct the 2nd level?


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I agree about the tank. I try to make sure mine have extra room to hide and be alone if they want to. That way there isn't any problems or fights over hiding spots or personal space to dig. I have 2 large and one small in my 40g now. They can be together whenever they want but also be alone to hide and/or dig in their caves. Better safe then sorry I feel..u remember when I firstgot mine I thought getting them 10g each was a huge upgrade because the pet stores say 5g a crab. I learned pretty quickly I needed more room esp with the stuff they should have in their tank.. And IKR.!!Jumbo shells are crazy. Not to mention when you pay for "jumbo" and get a med/large at best. I wish there was a place I could buy shells in person, atleast for the larger crabs.. and esp biggie claws. You just never know what your getting..is it large enough or will it have rough spots? I think trying to buy the larger shells is one of the biggest issues. I'm going to check out some of the links for shells