Recent Uptick in Aggression, Help me Figure Out Why
Posted: Sat Jan 16, 2021 11:29 am
Hi, everyone! I have experienced a recent uptick in aggression among my crabs and am honestly at a loss as to why. I don't consider this an emergency as I have already taken (what I believe to be) the necessary steps to curb the immediate issue. Was just hoping for some extra sets of crabber eyes to make sure I am not missing anything. 
1. What kind of substrate is used in your tank and how deep is it?
I am using a mix of EE and playsand. Mostly EE. It is 8" deep.
2. Do you have gauges in the tank to measure temperature and humidity? If so, where are they located and what temperature and humidity do they usually read?
Yes. I keep mine sitting on the substrate in the middle of the tank. I have been struggling a bit with heat this winter, currently sitting at 76 degrees Fahrenheit. Humidity is always 80%+.
3. Is a heat source used in the tank? If so, what?
Yes. I have two Ultratherms. One along the back that sits right above the sub line. Another on the side that covers the whole side from top to bottom. I only turn the side one on when the temperature dips too low to provide an immediate boost.
4. What types of water are available (fresh or salt) and how is the water treated (what brands of dechlorinator or salt mix and what ratio is used to mix it)?
Fresh and salt. I forget the dechlorinator I use, but it was one recommended on here. Instant Ocean for salt water.
5. What kinds of food do you feed and how often is it replaced?
A wide variety. Usually replaced every other day. Last night was: dried red shrimp, THCP basic diet, spirulina powder, crushed oyster shells, calendula petals, and icelandic kelp. There is always cuttlebone and leaf litter available as well.
6. How long have you had the crab and what species is it, if known?
The aggressive crab I have had for nearly two years now. All of my crabs are PPs.
7. Has your crab molted, and how long ago did it happen?
All of my crabs have molted several times under my care. I am uncertain as to the aggressive crab's last molt, most likely sometime around September 2020 or a tad earlier.
8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing?
29 gallon aquarium with a glass lid.
9. How many crabs are in the tank and about how large are they?
3 crabs. All are medium, 2 of them are pushing being a large. Nobody has moved into 1" opening shells yet.
10. How many extra shells are usually kept in the tank, if any?
Usually around 10-11 shells. Due to the recent events, I just added in extra. There are 16 in there currently.
11. Have there been any fumes or chemicals near the crabitat recently?
No.
12. How often do you clean the tank and how?
Spot clean as needed.
13. Are sponges used in the water dish? If so, how are they cleaned?
No.
14. Has anything new been added to your crabitat recently?
Nothing new has been added, see below where I explain actual circumstances.
15. Is there any other information you would like to share that might be helpful (anything that is regularly part of your crab care, playtime, bathing, etc.)?
No.
16. Please describe the emergency situation in detail.
I had a somewhat catastrophic sequence of events starting in the fall. A breakup situation made me move in with my parents temporarily. My ex took care of the crabs for a month as I *thought* I had secured a place to live and didn't want to move the crabs twice. He took decent care of them for someone who is not a crabber. He fed them a variety of dried foods and checked the gauges and changed out the water. The basics, essentially. Then my housing situation fell through and I decided to go ahead and move the crabs into my parent's place with me. That move was incident free. Nobody was molting, we did have to dig one up - but he was just chilling underground.
Then flash forward another 4-5 weeks, I found my own housing! I moved myself in and got settled, but held off on moving the crabs just yet as this was a bigger (approx an hour across town) move and I wasn't in a rush to get that done. Well my parents were not as good as my ex at taking care of them. When I would come visit the water bowls would be empty, dry food molded, etc. So yesterday we finally moved them to my new place (so this is their 2nd move in 8 weeks). All 3 were underground. We dug up one molter without a shell on. He was alert/active - but VERY pink. He was nowhere near his shell or exo - which leads me to believe he was attacked underground. I cannot think of another reason why he would have abandoned both his shell and his exo underground. I put him in a makeshift iso with his exo and shell. He took his shell back almost immediately. Other 2 crabs were fine, not molting. And so we moved them to my new place. I have the iso crab in a sealed tupperware sitting in the main tank, as I do not have the means to keep his separate enclosure warm enough. I cannot see him well and do not want to bother him, but he appears to still be in his shell and eating his exo.
Now today I heard chirping in the tank, look and see one of my older/larger crabs has my smaller crab upside down. Small crab is chirping, I intervene. Larger crab is locked onto smaller crab, will not let go. I had to gently shake him loose. I dunked larger crab in the fresh water to just startle him some and I moved along. Then less than an hour later I heard chirping again, I looked and saw the exact same scene. I intervened again. At this point the smaller crab went to the highest branch in the tank. I took all the shells out and rinsed them in declor salt water and I also added several more shells in. I haven't heard any more chirping or seen further aggression since.
But gosh, what gives? I have only ever had one other incident of shell aggression with this group and that was at a time where I certainly did not have enough shells large enough for the group. But now - ??? All I can figure is maybe stress from less than optimal care for the past 2 months? But even that care wasn't atrocious, they had a variety of foods and stable temp/humidity. Does anything in here stand out as a glaringly obvious cause to anyone? It's just super upsetting watching my group who has been together peacefully for so long suddenly have these issues.
1. What kind of substrate is used in your tank and how deep is it?
I am using a mix of EE and playsand. Mostly EE. It is 8" deep.
2. Do you have gauges in the tank to measure temperature and humidity? If so, where are they located and what temperature and humidity do they usually read?
Yes. I keep mine sitting on the substrate in the middle of the tank. I have been struggling a bit with heat this winter, currently sitting at 76 degrees Fahrenheit. Humidity is always 80%+.
3. Is a heat source used in the tank? If so, what?
Yes. I have two Ultratherms. One along the back that sits right above the sub line. Another on the side that covers the whole side from top to bottom. I only turn the side one on when the temperature dips too low to provide an immediate boost.
4. What types of water are available (fresh or salt) and how is the water treated (what brands of dechlorinator or salt mix and what ratio is used to mix it)?
Fresh and salt. I forget the dechlorinator I use, but it was one recommended on here. Instant Ocean for salt water.
5. What kinds of food do you feed and how often is it replaced?
A wide variety. Usually replaced every other day. Last night was: dried red shrimp, THCP basic diet, spirulina powder, crushed oyster shells, calendula petals, and icelandic kelp. There is always cuttlebone and leaf litter available as well.
6. How long have you had the crab and what species is it, if known?
The aggressive crab I have had for nearly two years now. All of my crabs are PPs.
7. Has your crab molted, and how long ago did it happen?
All of my crabs have molted several times under my care. I am uncertain as to the aggressive crab's last molt, most likely sometime around September 2020 or a tad earlier.
8. What type of housing are the crabs kept in, what size is it and what kind of lid is on the housing?
29 gallon aquarium with a glass lid.
9. How many crabs are in the tank and about how large are they?
3 crabs. All are medium, 2 of them are pushing being a large. Nobody has moved into 1" opening shells yet.
10. How many extra shells are usually kept in the tank, if any?
Usually around 10-11 shells. Due to the recent events, I just added in extra. There are 16 in there currently.
11. Have there been any fumes or chemicals near the crabitat recently?
No.
12. How often do you clean the tank and how?
Spot clean as needed.
13. Are sponges used in the water dish? If so, how are they cleaned?
No.
14. Has anything new been added to your crabitat recently?
Nothing new has been added, see below where I explain actual circumstances.
15. Is there any other information you would like to share that might be helpful (anything that is regularly part of your crab care, playtime, bathing, etc.)?
No.
16. Please describe the emergency situation in detail.
I had a somewhat catastrophic sequence of events starting in the fall. A breakup situation made me move in with my parents temporarily. My ex took care of the crabs for a month as I *thought* I had secured a place to live and didn't want to move the crabs twice. He took decent care of them for someone who is not a crabber. He fed them a variety of dried foods and checked the gauges and changed out the water. The basics, essentially. Then my housing situation fell through and I decided to go ahead and move the crabs into my parent's place with me. That move was incident free. Nobody was molting, we did have to dig one up - but he was just chilling underground.
Then flash forward another 4-5 weeks, I found my own housing! I moved myself in and got settled, but held off on moving the crabs just yet as this was a bigger (approx an hour across town) move and I wasn't in a rush to get that done. Well my parents were not as good as my ex at taking care of them. When I would come visit the water bowls would be empty, dry food molded, etc. So yesterday we finally moved them to my new place (so this is their 2nd move in 8 weeks). All 3 were underground. We dug up one molter without a shell on. He was alert/active - but VERY pink. He was nowhere near his shell or exo - which leads me to believe he was attacked underground. I cannot think of another reason why he would have abandoned both his shell and his exo underground. I put him in a makeshift iso with his exo and shell. He took his shell back almost immediately. Other 2 crabs were fine, not molting. And so we moved them to my new place. I have the iso crab in a sealed tupperware sitting in the main tank, as I do not have the means to keep his separate enclosure warm enough. I cannot see him well and do not want to bother him, but he appears to still be in his shell and eating his exo.
Now today I heard chirping in the tank, look and see one of my older/larger crabs has my smaller crab upside down. Small crab is chirping, I intervene. Larger crab is locked onto smaller crab, will not let go. I had to gently shake him loose. I dunked larger crab in the fresh water to just startle him some and I moved along. Then less than an hour later I heard chirping again, I looked and saw the exact same scene. I intervened again. At this point the smaller crab went to the highest branch in the tank. I took all the shells out and rinsed them in declor salt water and I also added several more shells in. I haven't heard any more chirping or seen further aggression since.
But gosh, what gives? I have only ever had one other incident of shell aggression with this group and that was at a time where I certainly did not have enough shells large enough for the group. But now - ??? All I can figure is maybe stress from less than optimal care for the past 2 months? But even that care wasn't atrocious, they had a variety of foods and stable temp/humidity. Does anything in here stand out as a glaringly obvious cause to anyone? It's just super upsetting watching my group who has been together peacefully for so long suddenly have these issues.
