couple questions...lights & rock displacement

[sirfishmaster]

does 3" depth make a difference with lighting? i am thinking of switching from my 55 gallon to a 40 gallon (& sump) the 55 is 21" high where as the 40 has same foot print is only 18" high.


2. how many pounds of rock will displace 1 gallon of water?



doug

 

[SquishyFish]

What kind of lights do you have? In general, I would say three inches deeper will not make a difference in your case. I will qualify that by saying that some high light corals such as SPS can be effected by a 3 inch difference if your lighting is already on the low side.

As far as the Rock displacing water...I have no idea what the ratio is. I know you will be effected as much by volume as you will weight. For example....if you put a one pound block of lead in the tank it wouldnt displace nearly as much as a fully inflated beach ball. Hopefully someone can give you a better answer.

 

[sirfishmaster]

i have 220 watt pc lighting 50% actnic and 50% 10,000K i really like the lighting but am leaning torwards MH but i close on house in Aug. then need a ro system....then illl jump the MH road.


doug

 

[copi]

Floating objects displace their weight in water. Sunk objects displace their volume. I doubt that helps any but it's one of those bits of trivia that I've been waiting to use, lol...

 

[DaveBeaty]

By volume (since "most" rock weighs more than water) 1 cubic foot of rock will displace 7 1/2 gallons.

Has anyone out there put weighed a 1 foot square chunk of limestone on a scale to see what it weighs? If someone could weigh a 1 inch square piece of rock I could run the math on it.

 

[RMPD109]

The problem is different rock has different densities and some are more pourous than others. The calculations may put you close enough to get an idea though.

 

[mybug]

How much weight from rock alone can a cheap 55G hold ?

I'm adding more base rock to my already present 55#'s of florida keys and live base rock from liverocks.com. I've got 40 lbs of Hawaiian base rock from Hirocks.com to add. Now I'm wondering if the weight is a problem.

Can my tank handle 85 or 95 lbs of rock sitting on the bottom ? Should I be worried about the weight ?