10 crabs in a 20 gallon tank

[Tonys Hermits]

I already have a 2nd story can I get away with having ten crabs or no most crabs are mediums

[Geranium]

If they are mediums, it looks like even with a second level, 9 is the limit. They will also soon outgrow it as they become larges.JMT wrote the following in the archived posts.Now, for rules of thumb, here are my observed limitations.Going by size of shell:Teeny = marbleSmall = quarter-50c pieceMedium = 50c piece-golf ballLarge = golf ball-tennis ballJumbo = baseballThese are my sizes. There is no widely held consensus on what constitutes different sizes.Any crab medium and above needs deeper/weighted water bowls, because they'll topply them when they dig if they are too light.5g: teenies only.10g: 2 large OR 4 medium OR 6 small OR 8 teenie20g: 3 large OR 6 medium OR 9 small OR 12 teenie30g: 4 large OR 8 medium or 12 small OR 16 teenie40g: 5 large OR 10 medium OR 15 small OR 20 teenie55g: 2 jumbo OR 6 large OR 12 medium OR 18 small OR 24 teenie75g: 3 jumbo OR 8 large OR 16 medium OR 24 small OR 32 teenie92g: 4 jumbo OR 10 large OR 20 medium OR 30 small OR 40 teenieThe tank needs to be at least 24in deep before I'd put jumbos in it, since they need 6in+ deep substrate, and big stuff to climb on, and not have the stuff they climb on reach the top, since they are strong enough to push open the lid and escape (ask Christa!)If you have a good second level, you can increase these numbers by 50%, since there is more second-level space to crawl and hide in, and with some of the crabs on the second level, there's more open substrate space to dig in.