mysterious sand and shell movement

lately some mounds of sand have built up and in other places the sand is almost down to the bottom pain of glass as well as some shells and other decorations have been moved. The inhabitants are 2 bicolor damsels, a 3 stripe damel, a domino damsel, an african moony, and 2 blue/green chromis as for fish and as for inverts i have a white leg hermit crab, a cleaner shrimp, and an emerald crab. the sand seems lowest where the damsels shoot through the rock work which is understandable but then there is also some random mounds of sand in the tank as well. i have a spongebob pineapple which always seems to move a few inches left or right and shells and some rock rubble have been moved from one side of the tank to the other. I'm 95% sure there is not a mantis or a pistol shrimp in the tank as well do to lack of popping noises and lack of sitings(the tank is in my bedroom so its near impossible that they could have done it when im not around). Recently one of my bicolors has been showing signs of being territorial/spawning by splashing up sand(not rubbing like you would see with ick) could he be the culprit? Could it be any of the other inhabitants in the tank? or what are some other theories of this phenomenon?

 

The way you described your sand being piled in one area sounds like the effect of water current to me. Try reorienting any power heads you have in the tank i.e. pointing them slightly towards the surface or so the current banks off a wall, ect... You may not see the sand moving before your eyes but a continues current will slowly move a pile of sand and leave you with an area void of sand in another place.
As far as the behavior of your fish goes this exceeds my knowledge and experience so cant make a comment on that.

 

I guess that could be it, but I cut down to 1 powerhead at night and it tends to happen over night at the opposite end of the tank from the powerhead and still doesn't explain the shells/rocks that well

 

I was going to say the same thing about current, and (total guess here) but I think that it would make sense that it would happen overnight in this situation. The current would change when you cut off the other powerheads, so the sand would end up piling up overnight differently than during the day. The sand would pile up (likely) on the opposite side from the powerhead since that's where I'd guess the current is weakest.

But, It is true that probably doesn't explain the rocks well.

 

maybe its a combinations of that and the hermit crab moving stuff maybe?

 

it could be. I know my crabs bulldoze everything!

 

I have nothing to add to this conversation

 

alright jerk, my 3 year old sister and 5 year old brother picked it out so go tell them thats stupid

 

Did I say it was stupid?

I'm curious... how do you keep it from getting crusted over with coralline algae?

 

I have a 29 gal QT tank that I have a bunch of damsels that I rescued. My domino damsel does this same thing. Now, a word to the wise. I don't like damsels in general (except a few exceptions), but I would suggest getting rid if the domino damsel. It is VERY aggressive!!!! My is also 3" and it chases all the other fish and it pretty much killed two fish already.

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