Odd Behavior From all Fish in Unison.

[ReefStuff]

Hi,
Been researching but having trouble finding a solution or cause. All of the fish in my tank will be swimming freely, then all the sudden all the fish, at the exact same time, will make a quick "scoot", down and away from the water surface about 1-2". Then immediately act as as if everything is fine and go back to cruising the tank. It happens pretty often, couple times an hour or so.
I assumed it was electrical so I tested the water with my meter. I have never felt even a tingle of electrical power in my tank when servicing it btw. Meter reads 38-40v. I have no broken gear, from my research this seems to be the induced voltage from the magnetic motors on the pumps. Lots of people seem to have about the exact same levels in the tank with no issue at all.
The corals have zero perceived reaction when the fish all do the scoot. I can not see any reaction from the inverts except the Cleaner Shrimp. The Shrimp makes a significant twitch when the fish scoot. It is VERY similar to when a loud step that scare fish when close to a tank. To be clear, No one but me is home and I am not moving, watching the tank for extended periods and observe this.

Water: (If Helpful)
Sal - 1.026
PH - 8.2
Alk - 8.5
Cal - 430
Mag - 1400
Nitrate - 10
Pho - .04
Temp - 78.5 F

 

[Tahoe61]

Strange.
Did you use live rock that might contain a Mantis Shrimp or Octopus?

 

[Uncle99]

What types of fish are doing that?

 

[ReefStuff]

Strange.
Did you use live rock that might contain a Mantis Shrimp or Octopus?

No,

It was all dry Marco Rock. Used the non colored typed. How likely would it be to get one of these as a hitchhiker on coral Frags?

All coral is dipped before entering my tank with Coral Rx and/or Lugos. Separately of course.


I sit and watch my tanks for long periods, I find them fascinating. Anyway, I have never seen any sort of “object” cause something the fish react to. Does not mean it is not happening though.

What types of fish are doing that?

Seemingly everything that is swimming in the water column. Chromis, Clown fish, Diamond Goby, Fire Fish, Blue Hippo Tang and peppermint shrimp. All at exactly the same moment. It happens too fast to see if one fish is some kind of “Leader”. Which was a thought I had, maybe they were following one.

Starfish, Nararius Snails, Conch Snail, hermit crabs, other snails and Coral is unaffected. At least don’t seem to be like the fish are. Never witnessed a “reaction” to anything really.


I do have one Acro frag that has done poor since the moment it was introduced. Soft coral and LPS are doing well. I only bring this up as I read Induced voltage can cause Closed Polyp and STN in Acro specifically. Well, it’s been in the tank for about 4 weeks and has always been closed and is slowly losing tissue. But, Tank is 6mo old, this was to test if the tank could support them yet knowing it was not really likely. I also did a poor job mounting and it fell 2x AND, my Alk swings too much with weekly dosing. Too many variables here imo. But maybe it is helpful.

 

[Tahoe61]

No,

It was all dry Marco Rock. Used the non colored typed. How likely would it be to get one of these as a hitchhiker on coral Frags?

All coral is dipped before entering my tank with Coral Rx and/or Lugos. Separately of course.


I sit and watch my tanks for long periods, I find them fascinating. Anyway, I have never seen any sort of “object” cause something the fish react to. Does not mean it is not happening though.

Seemingly everything that is swimming in the water column. Chromis, Clown fish, Diamond Goby, Fire Fish, Blue Hippo Tang and peppermint shrimp. All at exactly the same moment. It happens too fast to see if one fish is some kind of “Leader”. Which was a thought I had, maybe they were following one.

Starfish, Nararius Snails, Conch Snail, hermit crabs, other snails and Coral is unaffected. At least don’t seem to be like the fish are. Never witnessed a “reaction” to anything really.


I do have one Acro frag that has done poor since the moment it was introduced. Soft coral and LPS are doing well. I only bring this up as I read Induced voltage can cause Closed Polyp and STN in Acro specifically. Well, it’s been in the tank for about 4 weeks and has always been closed and is slowly losing tissue. But, Tank is 6mo old, this was to test if the tank could support them yet knowing it was not really likely. I also did a poor job mounting and it fell 2x AND, my Alk swings too much with weekly dosing. Too many variables here imo. But maybe it is helpful.

In my mind it seems like the identity of whatever is spooking the fish is a noise, a vibration.
It's entirely possible it could be a visual response to other fish posturing.
You could rule out equipment by systematically turning off each piece individually and patiently waiting and watching.

 

[damsels are not mean]

This sounds like a reaction to something a noise a silhouette outside the tank etc. Does is happen with nobody in the room?