HCA: Hermit Crab Association

Ok so I just got told by someone on a FB group that 3 crabs would be too many in my 20gal long setup....yet I've also heard the opposite...I'm confused now!!


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Giner13 wrote:Ok so I just got told by someone on a FB group that 3 crabs would be too many in my 20gal long setup....yet I've also heard the opposite...I'm confused now!!


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Hi, guess it depends on the size of the crabs/ length of time you have them. Personally 20 gals for 3 crabs sounds fine. I read a post on this forum suggesting 5 gals per crab. So you would be within those limits.

Layout, substrate depth, crab personalities should be taken into consideration too. I would not think it was a problem unless they were jumbo crabs that need a 12" depth and a 20g cant support that.

I don't think 20gal is going to be their forever home but it certainly will accommodate 3 sm-med crabs. Only time will tell for how long.

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Vic Future wrote:

Giner13 wrote:Ok so I just got told by someone on a FB group that 3 crabs would be too many in my 20gal long setup....yet I've also heard the opposite...I'm confused now!!


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Hi, guess it depends on the size of the crabs/ length of time you have them. Personally 20 gals for 3 crabs sounds fine. I read a post on this forum suggesting 5 gals per crab. So you would be within those limits.

Layout, substrate depth, crab personalities should be taken into consideration too. I would not think it was a problem unless they were jumbo crabs that need a 12" depth and a 20g cant support that.

I don't think 20gal is going to be their forever home but it certainly will accommodate 3 sm-med crabs. Only time will tell for how long.

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That's what I was thinking too. They're nowhere near large or jumbo size yet lol and even then I'd upgrade long before then!


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Giner13 wrote:

Vic Future wrote:

Giner13 wrote:Ok so I just got told by someone on a FB group that 3 crabs would be too many in my 20gal long setup....yet I've also heard the opposite...I'm confused now!!


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Hi, guess it depends on the size of the crabs/ length of time you have them. Personally 20 gals for 3 crabs sounds fine. I read a post on this forum suggesting 5 gals per crab. So you would be within those limits.

Layout, substrate depth, crab personalities should be taken into consideration too. I would not think it was a problem unless they were jumbo crabs that need a 12" depth and a 20g cant support that.

I don't think 20gal is going to be their forever home but it certainly will accommodate 3 sm-med crabs. Only time will tell for how long.

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That's what I was thinking too. They're nowhere near large or jumbo size yet lol and even then I'd upgrade long before then!


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Everybody has their way. I currently have 3 guys w 1" openings in a 10gal while i upgrade. I took the crabs well before I knew anything about them. My poor planning puts them at risk. I have my tank w 2 levels and luckily I have had no aggression. But it's not an ideal set up.

This forum is a great help. Good luck

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I have 2 med./lg. In a 20gl t

love my babies..human ones too!!

Many have their own sticking level suggestions. Even though I tend to go by surface area instead of total volume, a 20g long should be able to support 3 smallish (aka. Under large) crabs IMO.

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Yea they're still both under large size....reckon I'll give it some thought!!


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I think you would be fine as long as you follow the guidelines for substrate depth


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Giner13 wrote:Ok so I just got told by someone on a FB group that 3 crabs would be too many in my 20gal long setup....yet I've also heard the opposite...I'm confused now!!


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I had my 3 in a 20 gallon for quite some time, IMO they'll be fine. Every group has different beliefs. You just have to take in consideration the crabs size themselves.

I ditto all of the above:) I currently have 3 in a 20g tank and they are doing fine. They are all mediums.


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Thanks guys!!!!


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I'm currently still waiting for Peanut to come up topside in the old tank before transferring him. And I haven't seen Jack in about 2 weeks....lol I guess he decided his 4 month long molt wasn't long enough


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Personally i think that people get too caught up on the tank size when trying to determine how many crabs they can fit. Tank size is a good way to discuss the relative amount of space, but I think the more important thing to look at is how much climbing space, hiding spots, etc. there are in the tank. There seems to be a lot more vertical space in a tank than most people utilize. Large branches, climbing nets and sticks can be added to create more living space, (except for molting and digging, of course).

In my honest opinion, as long as the crabs have enough separate spaces where they can get away from each other, if they need to, and enough substrate burrowing/digging space, (like if every single one of them were to molt at the same time) you should be fine.

Also there are several Facebook groups that like to lay out hard and fast rules for crabbing, I believe partly due to the high volume of nubies they have to train, and partly because they just firmly believe that these regs are best for the crabs.

While there are a number of highly-specific substrate rules that seem silly in the context of what an animal may live with in the wild, I do happen to really like the 10gal minimum per crab rule. They are wild animals... but as stated above, climbing room is super imortant too.

Our philosophy at HCA (from what past admins have told me) is that a new crabber, who just learned that that $20 pet and kritter keeper they picked up, is not going to want/be able to spend a great amount of money at the outset to get a huge tank, and all the supplies that go into that.

We try to cover basics and prioritize substrate, waters, heat/humidity, food, and shells. Then we get into more specific things like hiding spots/climbing areas.

We try not to overwhelm new owners with the fact that a pet they most likely considered a short lived souvenier or easy beginner animal for their kids is actually a long lived and intermediate to advanced creature to keep.

Also, since the unfortunate reality is that no matter how awesome your setup is, starting out with a 75 gallon tank for some small/medium crabs (say you have 7 crabs, for the 10 gallon per crab suggestion) not all 7 crabs are going to make it.

So upgrading as you have funds or your crabs grow makes a lot of sense for many crabbers because, I think most of us can understand that it is disheartening to lose them (or any pet).

It also seems that crabbers are either lifers or have to give up the hobby around 2 years in or so.

At HCA we believe that there are no hard and fast rules of crabbing per se, that you do need basic survival conditions as mentioned above, but some methods work for one person that may not for another. Some people may need a fogger while others have great humidity without even needing bubblers.

I left every other crab group that I was in because the rigidity and the mass pouncing on new crabbers became too much. There have also been times when items that long term crabbers have used for years with no deaths or ill effects have been (IMO) blacklisted for use with crabs, even though people who have had their crabs for decades had no issues. (Correlation does not ever imply causation, sortof.)

PP's seem to be more chill being a little crowded (not super crowded) and get along well, while E's are known to become aggressive cannibals without enough space/substrate.

It all boils down to how your colony gets along and providing them with the best care you can and making sure their basic needs are met.

They don't need fancy isopods or bird houses or things that cost a lot of money. Many things can be DIY'd.

I can't tell you how many unopened free useless products I've received with adoptions that were able to be exchanged at the petstore.

Sorry for the novel but yes, as much space as you can give them is great, but if you aren't someone who makes it a habit to rescue/adopt every crab in the city (like me), and you just want to provide for the crabs you have, upgrade as they grow. It will save you money and space in the long run.

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