# Question about Crabs in Community Tank



## phishman123 (Aug 28, 2013)

So I have been considering for a long time getting a crab for my 10 gallon community aquarium. My question is what crab will be the safest choice for my tank? I know there is inherent risk in putting a crab in a community tank, I just want to know the safest option in terms of aggression, ability to harm other fish, etc. I have set my eyes on either a red claw crab or a fiddler crab so any experience or information comparing the two would be excellent. So I suppose my question is, what crab will be less prone to attacking and harming fish? 

Thanks!


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## J4C8_GreenGo (May 19, 2013)

I apologize in advance if I rant and rave and rage. I probably won't in this post, but if you ignore me I will.

Now, for my advice:

NEVER PUT CRABS IN A COMMUNITY AQUARIUM!

This really goes for any crab. The one exception is Thai Micro Crabs because those are truely aquatic. Most crabs need a decent sized land area and may burrow. So, realistically, this puts community aquariums out. I have never heard of a private community aquarium that is big enough to accomplish such a feat. Now, there are crab aquariums with fish, however, they are designed around the crab, not the community fish.

EVERY CRAB SHOULD BE IN A SPECIES ONLY AQUARIUM! (With VERY FEW exceptions.)

If you do put a crab in your aquarium, other than Thai Micro Crabs, I cannot stop you. However, without optimal conditions, they will suffer and live drastically shorter lifespans than in an optimal setting.


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## henningc (Apr 17, 2013)

I second the above. Go with a dwarf cray or shrimp.


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## phishman123 (Aug 28, 2013)

I had a feeling I would get this kind of response with the post I gave. I am well aware this is not an ideal setup to make but as far as the crab is concerned he's going to have a piece of driftwood (giving him several inches to hang out above the water) and an underwater crab habitat (giving him several inches of dry land below the surface) in additional I will be adding small amount of aquarium salt to at least somewhat provide some of the stuff it would get from brackish water. So I ask again, knowing full well this is not a perfect scenario, does anyone have any information/experience for me as to which type of crab (fiddler or red claw) will be better for my community aquarium? Thank you

P.S What about male vs female? I would definitely prefer a male but if I get good intel on how females would be better for my situation that would be great.


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## J4C8_GreenGo (May 19, 2013)

Okay, since you don't seem to get the point, I'll play along.... FOR NOW. As I play along, you will see full well why you should not do what you are saying you want to do.

So, you REALLY want a crab? Okay, fine. BUT, you shouldn't use aquarium salt. You need to use marine salt and get the salinity to ~1.005 to ~1.015. Yes, that salt for SALTWATER aquariums. You see, aquarium salt is for freshwater and is used in, I believe, treatments and such for freshwater fish. The salt DOES NOT have what the crabs need. Also, fiddlers need to burrow so they are out. They MUST have a land section.

Now, before you go out and buy a RCC please play along with me as I am with you. If not, and you go out and FOOLISHLY buy a RCC, prepare to get on my bad side. Trust me, you do NOT want to be on my bad side.

Now, a few questions for you:
1) What fish do you have?
2) Are you prepared to give the crab everything it needs to survive in your setup?
3) Are you prepared to take my advice and follow my instructions to the LETTER to ensure your crab gets the most out of life in a pathetic community aquarium? (Note: I will only condone this foolish behavior IF I see you are truely willing to follow my advice and not do something even more foolish than what you want to do now.)

Now, with that being said, I need your water parameters, fish in the aquarium and how many, any plants you may have, substrate type, and any other details you can give me on your aquarium.

DON'T BUY ANY CRAB UNTIL I SAY YOU ARE READY. Trust me, I only want to help, but in order to do that, you must listen to me and trust me.

The only way to get people to learn is to allow them to make their own mistakes. We have the capacity to learn from others' mistakes, but sadly we don't most of the time. I am willing to sacrifice a couple RCC for the sake of the greater good. :'( I am only willing to do this because they aren't endangered or anything. Also, don't think I will be this lenient all the time. 

I am very busy, but I will get back to you ASAP. I check this forum every day, and reply to any subscriptions/threads as necessary. There is a three day weekend coming up, so if we both get back to each other in a timely fashion, you may get my okay to get it by Monday. Just remember, don't get on my bad side.


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## phishman123 (Aug 28, 2013)

Sorry for the delayed response, I have been busy with labor day/work/etc.

I have 6 neon tetras and a betta, water parameters are all good(perhaps hardiness is a little low for a crab but I have cuddle bones), substrate is an aquarium sand (forgot brand name). I have 2 plants, swords and java fern. I think thats all the relevant info.

My betta almost exclusively stays on the side of the aquarium closest to me, and I plan on setting up the underwater crab habitat and driftwood that will give him a place above the water on the other side.

Thanks for the info about marine vs aquarium salt and fiddler crab burrowing. See I am already learning from you *w3


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## Jenniferinfl (May 3, 2013)

I would NEVER do a crab in a community tank. My husband gifted me a surprise Fiddler crab in my community tank. It had killed 7 of my 1" Apistogramma's before I got home from work. 

Get a Mexican dwarf orange crayfish instead. That's about the only one that would work in a community tank. The other crayfish are way too predatory. Even if you got lucky and got a crab that didn't consider your fish to be snack items, you could still measure it's lifespan in months rather than years in a freshwater aquarium as most of them are brackish water crabs. 

I get the desire for a crab, I really do. It was probably my 2 year old's favorite thing in the aquarium. We did move it into a 20 gallon long brackish water/land area aquarium of its own, but even so it died during a molt a week later, probably a side effect of being in fresh water too long. 

If you had a bigger tank that had been setup awhile, then you could consider a bamboo shrimp. They are big cool looking shrimp that are pretty much crayfish size but filter feeders. But, that won't work at all in a ten gallon tank. 

If you want crabs, do a 20 gallon long setup with a land area and a water area with brackish water like they require. I think Petco is running their $1 a gallon sale now. You will need a screen lid for a crab enclosure, they are amazing climbers. I used to find mine walking around on the aquarium lid and once it was running around the kitchen.


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## J4C8_GreenGo (May 19, 2013)

@jen: I agree with you on the whole community thing. However, sometimes people have to learn the hard way and other times people just don't have the money. RCC are actually fine without a land area as they are often in mangrove swamps and are thus on "driftwood" - the main reason I may allow phishman to get one. Also, RCC actually travel from fresh to brackish water all the time in the wild. The one thing I have a problem with what you said, is that it "had killed 7 of my 1" Apistogramma's before I got home from work." First, I would think the Apistos would've killed the crab and not the other way around. Second, crabs are too slow to catch organisms that are healthy. So, maybe they were going to die anyway. If not, it couldn't've been just your crab. Catching healthy fish requires a lot of time as they usually miss. So, I doubt it was your crab who killed all of them unless either: 1) they were already sick or 2) you were gone for at least a month - which is possible in some professions, but then that raises new questions. Now, do you have any proof it was the crab? Or are you just accusing a poor, unfortunate crab who may have just been in the wrong place at the wrong time?

@phishman: Now that I got that out of my system, phew. I would like to know your pH, Hardness, Gh, Kh, and temperature. I would like to cross reference a few reliable sources to find out if a RCC is appropriate for your aquarium. However, I don't think you can put marine salt in the aquarium, as it would most likely kill the plants and fish. As Jen said, they NEED a cover, as they are escape artists. And, no, a book over the cord doesn't qualify; as I found out the hard way.


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## Jenniferinfl (May 3, 2013)

J4C8_GreenGo said:


> @jen: The one thing I have a problem with what you said, is that it "had killed 7 of my 1" Apistogramma's before I got home from work." First, I would think the Apistos would've killed the crab and not the other way around. Second, crabs are too slow to catch organisms that are healthy. So, maybe they were going to die anyway. If not, it couldn't've been just your crab. Catching healthy fish requires a lot of time as they usually miss. So, I doubt it was your crab who killed all of them unless either: 1) they were already sick or 2) you were gone for at least a month - which is possible in some professions, but then that raises new questions. Now, do you have any proof it was the crab? Or are you just accusing a poor, unfortunate crab who may have just been in the wrong place at the wrong time?



They were Apisto juveniles and the fiddler was large, probably around a 2-3" leg span. I guess I assumed he did it because he moved into the bell decoration that half of them were using as a hide and he had one dead one near him and was eating another when I got home. Unfortunately I only had a few hides in the tank and the Apisto's are still at the stage where they are almost always hiding. It's pretty easy to catch something if your sitting in its home all day and it has a driving instinct to hide in that spot. I didn't lose any before he was placed in the tank and I haven't lost one since.


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## phishman123 (Aug 28, 2013)

pH is around 7.8, but I am expecting this to perhaps drop a little due to the new piece of driftwood I just added. I have no idea where my other hardness test kits are and the only one I could find was Kh which was....I want to say 500 ( it took five drops to turn it from yellow to blue...I know). Temp ranges from 78-82, usually on the higher side. Sorry I know that isn't everything you ask for but it's the best I can do atm. Now that I have the driftwood and crab habitat set up I am just waiting for the tank to recover and calm down before I go get my new buddy. LFS said they are getting a shipment of new RCC today and I'd like to get one as fresh as possible. I am still a little confused about adding salt to my aquarium. Is only marine salt beneficial to a crab? aquarium salt wont do anything? Is a small amount of marine salt very harmful for a fw aquarium? Thanks


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