Killer crab

[Lobot]

I need some help identifying and some advice on how to remove him. Earlier this morning i found him munching on a dead morsel which looked a lot like my new dragonet I bought Saturday 9/20. I was conflicted whether or not it was my dragonet because within the last week i noticed a royal gramma had disappeared and never found a body. Upon scaring him i discovered it was my dragonet. I believe he was killed in the night by the crab because i choose the fattest dragonet my lfs had and he was activly eating for the past two days. He showed no signs of parasites or disease. I noticed the dragonet was in the area i normally see this crab when my lights went. I only ever see the crab at night and he is always in a spot in which he looks ready to ambush something. The dragonet was the perfect prey because it was small, easily available because it was on the sand bed and it didnt know the tank very well.

I would appreciate any ideas on how to catch this thing because I want it out before it claims the life of any other fish.

 

[54seaweed]

that looks like a anemone crab i doubt he killed your fish just doing his job cleaning up
have you checked your water parameters
dragnets are fragile and the slightest change in water parameters can be lethal
i also noticed you have 11 post so i must assume your tank is new
are you sure your tank is even cycled

 

[Lobot]

I will check my parameters tonight, i did about a 15% water change on friday.
My tank is actually coming up on 7 months after cycle, i have been using my friend Beau_123 account to ask. I have done lots of research on these little guys so i was watching my pod population.
That picture was taken about 6 months and he is 1.5X bigger. I am concerned only because he has huge claws.

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[54seaweed]

still doubt he killed any thing , i have a lobster prob 10x the size of your crab if not more and never had a issue
but if they find something dead they will eat it for sure

 

[Lobot]

Ok. I'll have parameters later tonight

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[Sniperhank]

Crabs aren't the best hunters in the world. They are scavengers and opportunists. Can they catch, harm, or kill a healthy fish? No, especially not the ones you'll find in our aquariums.
Now, the fish you are showing is a scooter blenny. These guys are pod eaters and hard to care for. I had a green mandarin that I was able to get to eat mysis shrimp, which is hard to do, that was able to get him to survive for a much longer time than is to be expected...and even then they can simply stop doing so and only eat pods. It is more likely that he simply starved to death, though the part where you have seen him eat may challenge that bit, or that there was a parameter swing for whatever reason that gave this guy the TKO.

 

[Lobot]

pH-7.8
Ammonia- .05
Nitrite-0.0
Nitrate-0.0
Salinity-31
20 to 30% water change is going to occur in the next 2 days.
No need to be rude or anything but i have done a lot of research on the blennys or dragonets and i have been watching my pod population and it's been pretty consistent which is why I thought i would be ready to take on this challenge. I also choose the fattest one my lfs had to increase its chances of becoming established in my tank before it died of starvation. I think it was water parameters.

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[54seaweed]

your salinity is a bit high you should be in the 1.023 to 1.026 range
ph could be a little higher around 8.1 to 8.3
blennys / dragnets are a hard fish as so many things are required to keep them healthy the slightest swing could shock them causing a sudden death
also a risk of little to no pods to eat could cause starvation they can wipe out a whole population of pods in a day easy

 

[Lobot]

Well thank you both for your advice, looks like owning one of these will have to wait for the future.

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