For today’s post, I’m going to write about red-clawed crabs (Perisesarma bidens).
The red-clawed crab is a species of crab found in the Indo-Pacific region and can have a leg span up to 4″ and a carapace length of up to 2″.
These are small crabs that survive in freshwater, but they prefer brackish water, so you want to add aquarium salt that has been disintegrated in the water prior to adding to the tank.
They also thrive in water for 75-80F
But there are a few things that pet store employees may say that are not true:
- They can stay underwater forever
- They are great to have around fish and fish are too fast for the crabs to catch
- You can purchase a few for a 10 gallon tank
- You need to purchase an air stone and a filter for the red-clawed crab
- They are inexpensive to maintain
But I’m going to give you my experience of having a few of these red-clawed crabs and again, these are my experiences which may be different from others.
- They can stay underwater forever – I tested this in different aquarium situations and its true that they can live in the water for a long time but I actually caught the crabs looking for a place out of the water and one climbed above the heater in order to do that. So, we put a cave for it to climb and be out of the water. In another tank, two do not like to be under water and prefer to be on top of their rocks. But in general, they have to get 50/50 in water and a place to climb out of the water.
- They are great to have around fish and fish are too fast for the crabs to catch – We have a female in one community tank with different types of fish, where she can climb out in a mountain like structure to get out of the water. She has not killed any of the fish. BUT… we have a killer male. This one was put in the guppy tank and immediately, this crab killed as many guppies it can get its hands on.
Immediately, after adding the red-clawed crab to the guppy tank, there was one thing that I saw that was common. Each had their tails all gone.
At first, I didn’t want to think it was the crab because every forum started to say, the crab would grab and eviscerate the guppy and it would be shredded up.
But each day, one by one, a dead PREGNANT guppy with its tail gone as if someone came with a scissor and snipped its tail off and the sad thing, it appears that the guppy was dead after it gave birth to its fry. And somehow this crab knew when it was time to go after it.
I was able to rescue a good number of fry from each deceased female guppy but after a week…and seven days of guppy deaths, on day 7, I saw this…
It was going after the panda cordy and I had enough. I needed to catch this crab and these things are so good at hiding that it took awhile. But I put it in another tank with another red-clawed crab. Which I will discuss…
- You can purchase a few for a 10 gallon tank – Probably not…maybe one or two at the most but not more than that, despite these being sold with a few in a tank at the pet store. They are territorial and in this case, the red-clawed killer crab that I have, after moving it to crab tank with another female crab, both have now assumed their designated spot. One in one high rock colony and the other in another rock colony. Both spend their time above water and the killer crab, it likes to intrude in the other female’s side but she’ll try to defend it but in the end, the killer crab ends up winning the territory war and she goes to other other unoccupied side. But two is enough, adding another, I don’t know if that would end well.
UPDATE: That didn’t take long, the red claw crab killed the female crab two days after I posted this blog post.
- You need to purchase an air stone and a filter for the red-clawed crab – What you need is something to be above water for them to crawl and hang out. They like to stay in one place for a long time. Not the most exciting to watch unless they try to invade each other’s space but other than that, no air stone needed. As for the filter, nope. It just needs its periodic water changes. With that being said, I do use a sponge filter connected to an air pump. The reason being is that if you don’t do periodic water changes, you are going to get an insane smell that you are not going to like. So, it helps to have a sponge filter.
- They are inexpensive to maintain – Unless you have a 10 gallon tank around with a cover (these crabs can crawl out, so make sure they can’t), then you are going to have to invest in things where it can climb for dry land. May it be driftwood, rocks or decoration cave that allows it to get out of the water, these things all cost money. But it doesn’t need a pump or filter. Fortunately, red-claw crabs are omnivores and will eat shrimp pellets, fish flakes, brine shrimp or one of your fish that it catches.
In my experience, I learned that the female crabs (which have smaller and darker claws) are less likely to kill fish, while the male red-clawed crabs (that have the brighter red claws), it appears that hunting slow moving or still fish is something they thrive on.
So, if a fish is sleeping, resting after having babies or just going for a rest, just know that chances of a male red-clawed crab killing it is possible (or in my case, more probable in a daily basis). While I do have one female crab in a community tank, she hasn’t gone after any of the fish.
Otherwise, crabs are low-maintenance, are inexpensive and worth giving a try. But best to keep them separate from fish and if you want to get red-clawed crabs, consider making one tank a tank for that species.
