Why 2lbs live rock per gallon?

[searcher]

All my resources (books and the internet) state the a reef tank should have 1.5 to 2 pounds of live rock per gallon. I just wanted to know the reason. Is it just for looks? Or is there a scientific reason.
Just for clarity, I know the benefits of live rock. I want to know how that ratio was derived.

 

[2jz]

because most people cant afford 3lbs/gal
i guess its just a standard rule of thumb to guide people by.

 

[nicky1.8t]

i think its cuz live rock helps filter the water and to keep a stable reef you should have 2 lbs to filter the right amount. my guess

 

[thomas712]

Filtration would (I think) be the number one reason. However it depends on what you like to see, how many and what type of fish you want to keep. Tangs for instance would like to have swimming room and if you have a tank full near the top with rocks that doesn't leave much room for tangs let alone any other fish. Also water changes will come into play here, if you do a 20 gallon water change and expose your rocks with metal hallide lights going, well you can figure that out right? Simple matter of turning the lights off but why expose your rocks or corals.
Do what looks right to you and keep filtration in mind.
Thomas

 

[searcher]

Thanks for the responses. I went out of town for the weekend and forgot about this post.
It just seemed to me that lbs of rock per gallon is illogical. Just like watts per gallon when talking about lights. For example, suppose you had 15 lbs of rock in a 10 gallon nano which was able to support 2 clown fish. Then wouldn’t 15 lbs of rock support 2 clown fish in a 50 gallon tank? I think a better guide would be something like lbs of rock per inch of fish or type of fish one plans to keep.

 

[lesleybird]

I think it is all about personal tastes. All live rock is not equal as some is a lot denser and weighs more for the area that it takes up. Personally I am more into fish than corals (although I like a few easy corals), so I make sure that my rock work is designed with a lot of open spaces between and under the rocks so that they can play and hide. I also don't want to take away too much of their swimming room or total water volume. Some people who are really into corals just pile up mountains of rock so that they have more nooks to place more and more corals. This is great if all you have is mainly corals.....they don't need swiming room. I like a more open look with the live rock taking up not more than one third of the total tank volume. I like my fish to be able to swim under around and through the rock work. I like to make bridges with several smaller rocks on the ends under larger rocks so that their are multiple places for fish to swim under and through. I believe in trying to make the rock work be a work of art in itself, not just a pile! I really could not give an accurate guess as to the weight of rock in my 90 gallon. I have picked out each rock one piece at a time at my LFS by how it looked to me and how I thought it might fit into the total look of the tank. Lesley

 

[kreach]

Originally posted by searcher
For example, suppose you had 15 lbs of rock in a 10 gallon nano which was able to support 2 clown fish. Then wouldn’t 15 lbs of rock support 2 clown fish in a 50 gallon tank?
Yes, but in a 50 gallon tank, you will want to put more fish in there besides the two clowns, hence the need for more live rock as additional filtration.

 

[bdubbya]

The more rock you put in the tank, the more surface area the bacteria has to colonize on, i.e. better filtration. If you decide that you don't like the look of a rock garden, that's when you might consider other means of filtration, like bio-balls, bio-wheel and so on. Live rock also brings in natural sources of food for some fish. The more rock you have the better the chances something like a mandarin will survive.
Good luck.