05/19/2026
WHY THE 10 GALLON RULE DOESNT WORK
This is, of course, just an idea to provoke thought and is NOT intended to be a rule you should follow.
A standard 10 gallon tank is 20in x 10in, creating 200 sq in of floor space. Since the main objective of the 10 gallon rule is to provide enough safe space for a tanks inhabitants to molt, let’s say, for the sake of argument, that 200 sq in is the standard per crab.
In a standard 65 gallon aquarium, the floor space is 864 sq in. Using the 10 gallon rule, this is enough space for 6 crabs. However, using the sq in idea, this is only enough space for 4.32 crabs. Less for larger or more active crabs and species.
This is a large discrepancy when processing the math!
So which one is correct? I guess that depends on who you ask.
Many will defend the 10 gallon rule simply because it’s the standard practice, is in books, or is what the, so called, experts tell us to do. I would argue that if it’s a space requirement, the math provides the science in the form of sq inches, but I’m not trying to argue, simply to provide food for thought.
The thing about science and research is that it’s always changing as we learn more about the topic at hand. Those who stick to the books and are not open to the science progressing, or at least to the idea that it can be challenged, are doing themselves a disservice by not understanding and expanding their knowledge. Even if the new science isn’t exactly the answer, it can spark new thoughts, ideas, and ways of thinking that could help find the answer.
I’m curious to hear what your thoughts on this are in the comments. Thanks for reading!
