Ten Steps to Keeping Fiddler Crabs in an Aquarium

Have you ever wanted to own an Fiddler Crab? Thought it was too hard? Really, it's so easy and I'll show you exactly how it's done, step by step we'll delve into the fascinating world of keeping a crab and the rest of the fish in your tank happy!


1. How Many Fiddler Crabs

Fiddler Crabs need a foot of space for each one, more crabs than space and they'll either end up fighting all the time or else they'll lose their natural instinct to defend their territories. I have two crabs for my 10 gallon tank so plan your tank space accordingly. Males have one big claw and one small claw, females have two small claws. I have two females only and I've heard that if you purchase a male along with a female the male will actually do some interesting "dance" moves to try to get her attention.

2. Acclimatize Them to Your Water.

Treat them just like you would when bringing fish home, add a bit of water to the bag. I add a quarter cup of aquarium water, wait fifteen minutes and repeat. After that time you can net your crabs and let them go. NEVER pour the water from the fish store into your tank!

3. Feed Your Crabs.

As soon as you let them out. Reason being is because most fish stores usually don't feed their fish or invertebrates very well and your crabs are going to be hungry. Which means your fish are going to be in danger until you've got a happy crab. Feed your crab special sinking crab pellets or use any sinking pellet you happen to have on hand, sprinkle some flake food up there also. Your new crabs and fishes will thank you for it.

4. Your Crabs Need Salt.

Please don't believe some of the pet stores that say fiddler crabs are only fresh water! They are not. While they don't need all brackish water to live, they do need aquarium salt in there and the best thing is most fish find this beneficial also. However do check to make sure that ALL of your fish can tolerate a bit of salt in the water. There are fish out there that are VERY sensitive to water quality and you don't want to find this out the hard way. Also, under debate is the difference between Aquarium Salt and Marine Salt, you'll find people weighing in on both. I have found Aquarium Salt to be just fine, however, Marine Salt has more nutrients that would be beneficial to their shells and molting time. After reading over all of the nutrients in Marine Salt I'm actually going to try switching over to that instead. Last on the list is Please DON'T ever use Table Salt!!

5. Crab Proof Your Tank.

Crabs need both air and water to breathe. If you've got no way to get them air they WILL climb up pipes and tubing to get some. Crabs not only breathe air they also need the air to dry their shells out. One of my female crabs loves to climb the bio-filter pipe to get her air fix. I actually leave a little piece of cardboard over the tube to dissuade her from taking a tour of the rest of the house. A screen would work also, the ones you get for converting 10 gallons and up into a reptile tank, plus you can place the aquarium light right on top of that.

I also bought an Under Water Oasis, which is a bio dome that goes into my aquarium for my crabs, set up wasn't easy for my ten gallon tank, probably because I had to remove most of the gravel in the tank. I've found that my fiddlers climb less because they can just walk right in and have a little snack while drying out and breathing in fresh air.

6. Fish in the Aquarium.

Community fish, sounds boring doesn't it? That's far from the case! There are so many choices when it comes to community fish you're going to have a hard time deciding on a just a few. I went slightly out of the norm with my tank as I'd already had my fish established before I fell in love with a fiddler. My tank is a mix of slightly aggressive fish and community fish. Strangely not only do they all get along they leave my crabs alone. I do have a caution though, no mini or slow moving fish, also no long fins. My crabs seem to get twitchy around long fins, something about that flowing fin almost dares them to take a tiny chunk out. The reason for no mini fish is, because the crabs are less likely to try to grab a fish if it's bigger than their claws. I would also suggest no Moss Balls, my crabs really loved picking through it, until they tore it into little pieces.

7. Invest in a Heater and an Under Water Oasis.

Which you should have already if you've got fish. Keep the water between 75 and 82 degrees Fahrenheit and your fiddlers and fish will stay happy. Along with purchasing a heater, I also bought an Under Water Oasis. Which is a bio dome that I put on the floor of my aquarium for my crabs, set up wasn't easy for my ten gallon tank, probably because I had to remove most of the gravel, just to get it level. I've found that my fiddlers climb less because they can just walk right into the dome and have a little snack while drying out and breathing in fresh air.

8. FEED YOUR CRAB.

Sounds like I'm repeating myself? Because I am. Crabs will eat anything, including your fish, if you don't want them taking chunks out of your pleco, feed them several times a day. I usually feed them two to three small meals. Sometimes I will skip one of these feedings for the fish and simply drop just the sinking pellets in for the crabs. They will hunt for food for hours. I've heard they also like blood worms and other yummy treats and I do give those to my fish, however I've noticed that with hungry fish in your tank, not many blood worms or shrimp will get to the bottom. As a treat I also break up half of an algae wafer and drop several pieces in the tank, not only do my fiddlers love them but the fish seem to nibble on them as well..

9. Have A Hideout.

Because of the bio-dome I have, I don't have any hiding places. Hideouts can be simply bought at your pet store, look for regular aquarium decorations and I'm sure you'll find something you like. Or you can make your own by putting in a piece of driftwood or adding some rocks. It really is easy. Your fiddlers will appreciate the "fortress" and eventually they are going to molt. When they lose their outer shells they will be vulnerable until the new one hardens. That's the time your crabs will need to be sheltered away from picking fish. Also leave the exoskeleton in there for a week or two because it contains calcium which your fiddlers will feed on.

10. Watch Your Crab.

That's right, you've done everything you can to make your crab or crabs welcome and the fun part is taking some time to relax and watch their antics. Females and males will argue over territory, tussling with their claws until one of them gives up and goes to another part of the tank. Not only will you get minor arguments like that, they are fascinating to watch. Eye stalks go up and down, claws nip at body parts, and bottom plates open up. So now that you've done all the hard work, it's time to sit back and enjoy your fiddlers!