Do I still have a killer in the tank?

mtconnol · Nov 17, 2018

So I'm a week into setting up a reef tank for the first time. I have a 90 gallon tank with a sump and started with the 75 gallon Package from Tampa Bay Saltwater. So far I only have the first half of the shipment, and it was definitely teeming with life! Perhaps too much life...

The rock has been popping and clicking incessantly since it arrived. I know that this is most likely pistol or mantis shrimp - I did successfully trap a 3" mantis, which I was astounded had somehow hidden inside the rock while I inspected it. That guy is gone to the LFS, but the clicking and popping remains. Today I fished out a 1" wide gorilla crab which appeared to be dead from a crushed shell. I have also seen broken snail shells, but it's a little hard to keep track since the live sand had crushed shell to begin with.

The rock was teeming with barnacles when it first arried, but most seem inactive now, a week in. I started feeding Micro Vert every other day to try and keep them alive, but I don't know if it was insufficient or something has eaten them. Some of their holes seem wider, potentially broken open.

I just pulled out two large Lace Murex snails as well.

So it seems like there's still a killer on the loose in there?

The 'bay scallop in a pint glass' turned up nothing.

There is a lot of cute life on the rock, including what I think is a sea squirt, some nice coralline, and some tiny corals. I don't want to kill everything on these rocks in trying to flush more mantis or pistols out, but don't know what to do. I read mixed opinions about whether club soda or fresh water will successfully flush the predataors or just kill everything along the way.

It seems silly to get the second shipment of rock before trying to get this more under control.

Please help! I am trying to get everything set up right in this tank, but am feeling pretty overwhelmed. I don't want all the good life to die while I sort this out.

ndrwater · Nov 17, 2018

The snapping is Pistol shrimp, very common. I agree in holding off the shipment #2 for a bit. Unfortunately, it is possible you lose a bunch if the "life" on the rock initially, but don't be deterred. What seems to die off oftentimes makes a miraculous come back.
Keep dosing the bacterial cultures, it'll definitely help.

mtconnol · Nov 17, 2018

ndrwater said:
The snapping is Pistol shrimp, very common. I agree in holding off the shipment #2 for a bit. Unfortunately, it is oossipos you lose a bunch if the "life" on the rock initially, but don't be deterred. What seems to die off oftentimes makes a miraculous come back.
Keep dosing the bacterial cultures, it'll definitely help.

Thanks for the response. One confusion for me is whether the snapping and the predation are one and the same. I have never actually visually caught anything snapping, but given the size of prey being taken I have to imagine the predator is sizeable. The 3" mantis I took out was not hiding in the least, just strutting around in broad daylight.

I have read mixed opinions about whether the pistol shrimp are actually dangerous to other creatures. What do you think?

ndrwater · Nov 17, 2018

They are normal on a wild reef. Snapping to defend territory and or attract a mate. With time, I think this will subside in a captive environment.
There are many different tyoes of predators that can show up in live rock. Mantis, Eunicid worms, gorilla crabs just to name a few. Pull the ones you can, banish them to the sump, cross your fingers for the rest. Real deal live rock like you got is a blessing and a curse all at the same time. The benefits of all the micro and macro fauna will reap rewards long term. Short term, some of the "less desirable" things like some of the aforementioned pests can be difficult to rid yourself of in a small captive system.