Tank strength?

[Bling]

I've been admiring a lot of your tank setups, and I'm wondering about all those big rocks I see. What's the weight limit to the glass floor of the aquarium? Mine doesn't actually rest on the glass, but is set into a frame, which seems pretty standard, so all the weight really is borne by the glass. Or are those rocks plastic? Has anyone ever used Skulpy or Fimo for making decorations? They wouldn't weigh much.

 

[Ava_Banana]

As my glass base is on a flat wooden surface (with a soft layer inbetween) the weight is spread by the gravel........then the UGF then the glass, then the soft layer, then the stand.

 

[SirMinion]

Never really thought about it.
I suppose that the tanks are designed to take the weight, so it's not something I've worried about.

 

[Final Dynazty]

Yeah i wouldn't worried the bigger the tank the thicker the glass.

 

[Da_Oz]

Some rocks aren’t that much heavier than the water it replaces. Water is about 8 pounds per gallon. So in some cases the rock is taking up a gallon worth of water and only has a weight of 10 to 15 pounds. So really your only adding 2 to 7 pounds spread out over a area. Another thing to look as a rock is not a free floating liquid so its force is not measured the same as water.

 

[gadazobe]

Doesn't the theory that the weight of the water displaced by an object is equal to the weight of the object itself work here. If you put in rocks weighing 10lbs then the weight of the water displaced will be 10lbs so there is no difference in the weight of the water with rocks or without rocks.........I think. Archemedes theory when he was in the bath.

 

[fraservet]

my physics is a bit rusty, but I think it's volume of water displaced equals volume of object displacing it, not weight

i.e. if you put a hollow ball (obviously watertight!) into a tank, it would displace as much water as a solid ball of the same size, but would be much lighter.

- and before anyone says anything, this is just a simplified example, I know the hollow ball would float etc.

 

[Zagggon]

Yeah for my 42gallon hex aquarium i called oceanic which is the company i got it from and they said that my 40 pound lime stone rock would be just fine on the glass bottom, they even said that if you wanted you could easily put a 100 pound rock on the tank, they sounded pretty confident.

 

[gadazobe]

my physics is a bit rusty, but I think it's volume of water displaced equals volume of object displacing it, not weight

You're right - sorry ) I knew it was something like that.

 

[Da_Oz]

Some SW tanks have 100's of dry pounds of rocks in them.

 

[schizo_fish]

also, as far as im aware objects weight less in water than they do out. due to the force of the water acting upwards.

 

[K-Holed]

Density = mass / volume. The denser the rock you use the more it's going to weigh size for size. Also, as has already been mentioned by schizo_fish, when a body is completely or partly immersed in a fluid it experiences an upthrust, or apparent loss in weight, which is equal to the weight of fluid displaced.