HCA: Hermit Crab Association

I was looking through posts trying to figure out the best way to change out my substrate. The substrate i have currently has been in there for about 2-3 years. I didn’t do enough research at the time and used a 1:1 ratio of sand and coconut fiber. I also don’t have enough, it’s only about 3 inches deep at the moment. I have recently fallen down the rabbit hole of proper hermit crab care and I want to make sure I am doing it right from now on. I thought I would change out the substrate to get the right ratio, and also because I have noticed the crab’s waste and bits of old food have started to accumulate on the top. While browsing through posts I saw that some people never change their substrate and just add more on top. For my case, because of the improper ratio and waste/food buildup, would it be wise to just change it all out?
Follow up question - I know that 2/3 of my crabs are under the soil right now, one has been under for almost 2 months and the other just went under. I am not planning to change the substrate at the moment because of this. But given that I have 3 crabs and they all molt at different times and rates, how do I time it right so that I am not disturbing their molting process? I would like to take the steps to make sure they have ideal substrate as soon as I can, so I’m a bit stressed trying to figure out how and when to go about it.

I’ve used the 1:1 ratio in the past without problems, and as for the waste accumulated you can just scoop and spot clean as needed

If you’re not happy with your substrate though it would be easiest to wait for everyone to be up at once, even if it can feel like a mad scramble to finish before someone starts digging again

If you don’t want to remove everything and just add more (using whatever ratio you decide) you can gently add more on top, but be careful not to pack it down or you risk collapsing burrows

I’m one of the people who don’t change out their substrate, but I do churn it up to aerate it once a year

In my opinion you can get away with using what you have and just adding more substrate to meet depth requirements, but I would scoop up the waste first so it’s not decomposing at the bottom of your tank


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I am one of the people who never changes sub, just adds more and mixes it up now and then.
There are other long term crabbers who do change it out every year or couple of years.
There is no 'right' or 'wrong' ratio of sand and coco fiber, all one or all the other or a mix in any ratio are all 'proper'.
Most of us do remove the poop and bits of food that we see accumulate on the surface, this can be done even with crabs underground. Otherwise, if you want to do a full substrate change, you either need to wait until they are all above ground or you need to dig them up to do so.

Joe was replying at the same time I was LOL!

Thank you Joe and curly sister for the responses! It’s good to know that the ratio isn’t as strict as I thought. I will plan on scooping and throwing out the top layer and just adding substrate on top.

If you don't want to clean up all the poo, you can add a clean up crew like isopods or springtails.