[anthias]

Lee it is me again
I have athinking about two things that could be additional source of stress:
1- vibration caused by powerheads (if u but ur hand on it u can feel it)and that for sure will produce magnetic field.
2-noise coming from air pump and fillter.
I can easly hear the noise of the big fillter under the tank and when I but my ear on the tank wall I can hear and feel the vibration.

[leebca]

I think you have something there, with the vibration stress. Not too sure of the magnetic stress. There's a key question yet to be resolved/answered, though.

Marine fish have 7 senses. One of their extra senses is the ability to sense vibrations. In fact, that is one of the functions of the lateral line.

Fish in the wild and in our aquariums can pick up vibrations and each other's signals. As I wrote in some other post (somewhere) one of my fishes learned how to scatter the other fishes at feeding time. When I dropped the food in, the 'tricky' fish would send out a 'warning signal.' The other fish would swim away and hide while that fish stayed and gathered up a lot of the food!

I've also seen fish react to other fish they can't see, and yet are in the same aquarium system. For instance, a fish at the end sends out a distress signal and the fish out of sight swim away fast and hide. They do indeed sense vibrations.

But the key question is, 'Is that important?' In the sea/ocean there are plenty of vibrations that are, more or less, natural. The pounding surf, water rushing through the rocks at tidal changes, marine life that makes noises/sounds, etc.

There are certainly other sources of sounds/vibrations associated with our aquariums -- ballasts from light fixtures; pumps (system pumps); skimmer; chiller; and external sources (people walking, music, people talking, A/C & heater units, etc.).

[anthias]

I have a bicolor angel hidding all the time , it only rises from its place when I switch the fillter off.
isnt better to but all these machines in a separated cabinet??
you know I am rearranging my display tank,I realy trying to do my best to have astress free aquarium,maybe one day I can say : I have 20 years old display tank free of diseases and parasites.
I am waiting for my new skeemer coming from the US .
and if you can help telling me how to arrange the water stream(under the water)
best thanks

[leebca]

One system that reduces vibrations in the display tank utilizes a separate tank called a sump. The display tank water runs by gravity into the sump and in the sump, a pump(s) called a 'system pump' returns the water to the display tank. Now, all the equipment is in the sump, outside and away from the display tank. Another benefit of the sump is that it will add water volume to your system and this will add to the stability of the water quality and slow down changes to the water chemistries.

In the sump you can put the system pump(s), filters, skimmer (and skimmer pump), heater, chiller, etc. Some people put their sump many meters away from the display tank like through a wall into another room or ventilated closet, or even on a floor below (like a basement) the display aquarium. A refugium can run off the sump by taking sump water, running it through the refugium and returning the water from the refugium to the other end of the sump.

Regarding the behavior of the angelfish, you should make sure that your pump isn't 'leaking' electricity. You should check for an electrical problem and verify that the fish tank isn't getting any electrical current through it.

Are electrical outlets and equipment where you live grounded or is there a provision for grounding?