HCA: Hermit Crab Association

We've had our crabitat for 1 year 4 months. I'm somewhat ashamed to say I have never really cleaned it! We have 3 crabs in a 15 gallon tank, well, actually I am pretty sure only 2 now . Up until recently there always seemed to be a crab buried so I felt I couldn't disturb the substrate. The tank doesn't smell bad or anything, I am just starting to wonder how long can it go on without being cleaned. I have read some posts about adding Isopods. That seems too good to be true, but I would love to try it! Since the 2 crabs have been up and very active lately (like since Spring began) I am considering doing some cleaning now. It's not like I haven't done any cleaning-- all along I have removed old food that has been dragged around the tank. At first I tried to scoop the poop with a plastic spoon, but with the substrate being so dark and the worry over disturbing the crabs I just kinda stopped. Please advise!

If you have appropriate substrate, it very rarely needs to be completely replaced. Some people do every year or two. Personally, I have had my crabs for 9 1/2 years and have never changed out all the sub. I have added more as I upgraded tanks and as my crabs have grown to keep it deep enough. I scoop out bits of rotten food etc but that's it.
I use the approx 5 parts play sand to 1 part EE mix for my sub.

Ya I think that unless there is a bacterial bloom or some sort of fungus or mould I think it will be ok sorry this is a little off topic but a lot of people have been saying that there hermit crabs poop. I have not seen anything that looks like poo to me.lol I have had mine for about 4 months. Am I missing something?


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I am just worried that it may be rotting. And like is it big? Sorry the questions are a little weird but I was just wondering. Lol


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Crab poop looks like little brown miniature noodles, very small like about 0.5mm wide by 3-5mm long. If you have a lot of EE, it will be hard to see.

i loved your description “little brown noodles.” LOL!


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Wow! Thank you so much! Yeah, the poop is hard to see in the dark EE, but since there's no smell I guess I won't worry about it right now.
I am planning to add some new substrate to fill in some low areas soon.

I'm partial to the term "Brown Frowns!"

We have seen crabs eat their poop or from others. Crabs are weird and gross!

So what about Isopods? Not necessary? Do people just get some roly pollies from the yard and put em in? My kids would like that, but I wouldn't want the rollies to get too numerous...

You can collect isopods from your backyard. If you do is is best to keep them in a separate tank or tote for several months to detox them. That will reduce any chance of pesticides or other germs being released into the crabitat.

The plus side of that is as they over populate you can safely release them into your yard. You can't do that with isopods ordered online. Isopods are demons to some, angels to others!

Aside from routine thinning of the numbers no additional cleaning should be required. If you decide you no longer want them they are very difficult to completely remove.

Interesting. I know my kids would love to add some rollies. What you described reminds me of tiny snails being accidentally introduced into aquariums on live plants. When I had aquariums it became a real nuisance, picking out all the snails each water change and basically throwing them away, only to have a brand new crop the next time. Anyway, thank you for your response!

Motörcrab wrote: ↑

Mon May 11, 2020 2:46 am

I'm partial to the term "Brown Frowns!"

We have seen crabs eat their poop or from others. Crabs are weird and gross!

Haha! These are most commonly found in the food bowl in my tank . My crabs are so lazy they can't even get out of the bowl!
I haven't cleaned my sub(besides spot clean, etc) fully for 2 1/2 months or so (mostly bc my crabs keep going up and down) but the crabitat seems to be doing fine (and I have no isopods, because the fam would go nuts).
And Motör, I think we can all agree that part of the reason why we love our crabs so much is because they're weird and gross
Edit: Forgot to ask, Mitt, how long has your crab been down for? How big is s/he?

I'm with Curlysister - I've never changed my substrate. I just add to it because it gets packed down over the years. As far as cleaning the tank...I just change my waters once a week, change my food daily.

I do have isopods. I originally added 20-30 to each of my crabitats. I have helped populate a good handful of members here on the HCA for free, from those. They bred OUT OF CONTROL. They eat my crab poop, my crab food, and my moss. LOL! I love watching them, but I'm constantly emptying them from my crabitat into a 65 gallon storage tote. I sell them to a reptile store now. If you get some....LESS IS MORE!!!

When I started with a 10g, I cleaned it once a year and kept half the substrate to 'reseed'. Honestly, I've never fully cleaned out the 20g we currently have and I had the 55g for 4 years and never cleaned it out until we had to for a move.

If you have Eco earth substrate, it breaks down a lot of the waste product. When my mix was mostly sand, I had to do a lot more scooping and spot cleaning but now that it's 70/30 eco to sand, I don't even bother scooping unless food goes missing.

That being said, if you're worried that you have a dead crab buried (I'm unclear on that from your post) you should definitely dig up the body and dispose of it.