HCA: Hermit Crab Association

Why do some groups believe a 29 Gallon is superior to a 20?

29 Gallon tanks are 6 " taller than a 20 gallon tank. You would be able to fit a crab more.

29G measures 30x12x18 (LWH)
20L measures 30x12x12 (LWH)

You can offer deeper substrate and still have plenty of climbing room left using a 29G...
In a 20G once you add 8 inches of sub, that only leaves them with 4 inches of climbing/walking space. In a 29G, it would leave the crabs with 10 inches of climbing/walking space.

I have a 20L (now a guppy tank) and a 29G (now an ISO tank). Definatley prefer the 29G over the 20L.

Edit: you can do more decorating with a 29G vs a 20L. Things just seem to fit better!

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Yep, since it is the same sized rectangle it fits in the same amount of space, and the top and supplies for inside cost the exactly the same as the smaller 20. Deeper tank, more room for substrate and decor. It's also a very pleasing tank aesthetically, it doesn't seem cramped or too tall. I used one for my fiddlers and loved it, and my Ruggie is getting that tank once I get the stand painted.

AwesomeHermit wrote:29 Gallon tanks are 6 " taller than a 20 gallon tank. You would be able to fit a crab more.

You cannot necessarily fit more crabs into a 29 gallon, but you can provide deeper substrate.

Footspace is the same as a 20 g.

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soilentgringa wrote:

AwesomeHermit wrote:29 Gallon tanks are 6 " taller than a 20 gallon tank. You would be able to fit a crab more.

You cannot necessarily fit more crabs into a 29 gallon, but you can provide deeper substrate.

Footspace is the same as a 20 g.

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Well if you are to go by the 'gallon per crab' rule (5g = 1 crab) then you could fit in more. But realistically they offer the same amount of space so your better off understocking and allowing ample floor space per crab.

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aussieJJDude wrote:

soilentgringa wrote:

AwesomeHermit wrote:29 Gallon tanks are 6 " taller than a 20 gallon tank. You would be able to fit a crab more.

You cannot necessarily fit more crabs into a 29 gallon, but you can provide deeper substrate.

Footspace is the same as a 20 g.

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Well if you are to go by the 'gallon per crab' rule (5g = 1 crab) then you could fit in more. But realistically they offer the same amount of space so your better off understocking and allowing ample floor space per crab.

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Yeah I thought of the gallons per crab recommendation.

Sometimes I wonder if we should consider substrate volume and molting space moreso than overall tank size, but my neurodivergent brain gets caught up on weird things sometimes.



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soilentgringa wrote:

aussieJJDude wrote:

soilentgringa wrote:You cannot necessarily fit more crabs into a 29 gallon, but you can provide deeper substrate.

Footspace is the same as a 20 g.

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Well if you are to go by the 'gallon per crab' rule (5g = 1 crab) then you could fit in more. But realistically they offer the same amount of space so your better off understocking and allowing ample floor space per crab.

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Yeah I thought of the gallons per crab recommendation.

Sometimes I wonder if we should consider substrate volume and molting space moreso than overall tank size, but my neurodivergent brain gets caught up on weird things sometimes.



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Haha, i tend to view floor space more important than volume, since they dont have access to all areas of the tank like a fish would... they only have access to the surface area we provide (except digging room, but even then my crabs all tend to dig as far down as possible....)

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Ideally, you want the substrate depth to be three to four times that of your largest hermit crab's shell for digging and molting. In addition, crabs love to climb things, so the more height you can give them above the substrate, the more places you can give them to play. I just had our four crabs in a 29 gallon tank until last night because it was the tallest affordable tank I could get at the time that met the gallons per crab guidelines. The 29 gallon tanks are easy to find and occasionnally go on $1 per gallon sales at pet stores, which also helps them be such a popular choice. For our crabs, the substrate depth (8 inches) was adequate though not exceptional. That said, all our crabs have molted in our 29 successfully. Some more than once. But the space above the substrate still felt constrained and I'd often find crabs hitting their shells against the underside of the lid after climbing our ornaments. That said, we have hermies on the larger side.

My mom seems to be stuck in the 'crabs don't need a lot of space' myth and will not let me upgrade to a 29 Gallon unless my crabs are the size of my fist. My crabs are still medium size. One of them just molted and the other one is gearing up for a molt. I've tried to tell my parents that my crabs are going to grow but that falls on deaf ears.

crabby33 wrote:My mom seems to be stuck in the 'crabs don't need a lot of space' myth and will not let me upgrade to a 29 Gallon unless my crabs are the size of my fist. My crabs are still medium size. One of them just molted and the other one is gearing up for a molt. I've tried to tell my parents that my crabs are going to grow but that falls on deaf ears.

Oh no can you print out our tank size recommendations for them?

Fist size crabs would need an even larger tank, as jumbos should have an 18" wide habitat for legroom.



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