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How many pounds of dry rock per gallon?


rev138

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I'm starting a new tank (see second link in my sig) using dry coral rock which I will seed with a few small pieces of LR.

 

I know the general rule for LR is 1-2 pounds per gallon, but being so porous, LR is saturated with water, and much of that weight must be H2O.

 

I was wondering if there's a rule of thumb for how many pounds of dry rock to use per gallon?

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Hey, one at a time guys! Don't all answer at once :P

 

I have no personal experience as I'v used LR with each of my 2 tanks... however I've been planning on getting some dry rock myself and reading up on it a bit, from what I'm reading I'd say it about doubles weight once wet.... for my 50g I'm going to order a box of 25lbs of dry rock and go from there.

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I guess my 12lbs for my 20g should do then. A lot of the chunks are just large masses of feather duster tubes, so they're extremely lightweight and porous.

 

Good deal :)

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hey bro i have a 10 gallon that i seeded with 2 lbs live rock and five pounds of dry rock. I was curious after i read this post so i picked it up and had a 5 lbs weight in my other hand and i figure the rock was around double the weight. so hopefully that gives some estimate. (If you trust my weighing skillz.)

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can't really go by pounds per gallon.

 

some live rock is much heavier and dense than other. like for example tonga branch will fill up a tank with less poundage than fiji would. just get enough in there to give the desired look and still have some surface area to be benificial to the system.

 

xoxo

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some live rock is much heavier and dense than other.

 

I thought this was the reason for the 1-2 pound guideline. 1 pound for light rocks, and 2 pounds for denser ones.

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I guess my 12lbs for my 20g should do then. A lot of the chunks are just large masses of feather duster tubes, so they're extremely lightweight and porous.

 

 

So you settled on almost half of what you think the guidelines recommend?

 

:huh:

 

I'd stick to the guidelines. The high surface area of highly porous rock means less of an anaerobic environment available for denitrifying bacteria. As a matter of fact, I'd use double the guidelines for highly porous rock.

 

Considering that high nitrates is a more common problem than high ammonia, an anaerobic environment and denitrification is a greater consideration than surface area for aerobic bacteria and ammonia oxidation. In my opinion, of course.

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So you settled on almost half of what you think the guidelines recommend?

 

:huh:

 

I'd stick to the guidelines. The high surface area of highly porous rock means less of an anaerobic environment available for denitrifying bacteria. As a matter of fact, I'd use double the guidelines for highly porous rock.

 

Considering that high nitrates is a more common problem than high ammonia, an anaerobic environment and denitrification is a greater consideration than surface area for aerobic bacteria and ammonia oxidation. In my opinion, of course.

 

MR A He put dried rock in the tank which will be considerably lighter than the live rock rule of thumb.

 

Rev a way to get an idea is to simply soak your rock and weigh it. You have more than likely already done your aquascaping and probably like the way it looks. If it looks like you have a good bit of rock in there and you like it leave it alone. Once your rock turns live nobody needs to know exactly how many pounds of rock you have. I'll bet that none of us know exactly what we have anymore anyays espcially after we started fragging crap here and there.

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formerly icyuodd/icyoud2

the rule for lr is based on the amount of lr required to filter set amount of water. (just a rule of thumb, not set in stone)

 

since your dead rock hasnt the ability to filter your water, theres no rule of thumb for how much should be in the aquarium. you can add as much or as little as you like. until its completely seeded its not doing much for you either way.

 

my advice to you, your lr is the most important part of your reef. not only should you ditch the dead rock and purchase live rock, but you should also purchase top quality rock.

 

cheaping out and filling the tank with dead rock, will only cost you more money in the long run.

 

lr is the one thing in a reef tank, you shouldn't cheap out on. and imo buying rock online is just foolish. i hand pick every rock thats entering my system. i look for cool shape,porous rock, and a variety of life on/in the rock.

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HecticDialectics
my advice to you, your lr is the most important part of your reef. not only should you ditch the dead rock and purchase live rock, but you should also purchase top quality rock.

 

cheaping out and filling the tank with dead rock, will only cost you more money in the long run.

 

lr is the one thing in a reef tank, you shouldn't cheap out on. and imo buying rock online is just foolish. i hand pick every rock thats entering my system. i look for cool shape,porous rock, and a variety of life on/in the rock.

 

Not true at all. It's very possible to buy dead rock that is much higher quality than any live rock in a comparable, or even close, price range. The only down-side would be lack of diversity, which is completely avoided by properly seeding the tank, and a slightly slower stocking time, which isn't really a problem. Getting a nice coral hitchhiker is like getting struck by lightning unless you buy some TBS lr or something for a nice bit of change.

 

Cheaping out and filling the tank with crappy dead rock... solid blocks of fiji, lace rock, lava rock... will probably cost more in the long run, but there are CERTAINLY ways to get very nice rock economically. Not everyone wants to pay $10 a pound and go into debt for what may or may not be nice local rock.

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As a matter of fact, I'd use double the guidelines for highly porous rock.

 

That runs counter to everything else I have read. All my research says that you can get away with less poundage if the rock itself is less dense.

 

Anyone care to comment on this?

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That runs counter to everything else I have read. All my research says that you can get away with less poundage if the rock itself is less dense.

 

That's not too surprising. Online "research" will also tell you things like "there is an inverse relationship between calcium and carbonate hardness" or "solve low pH by adding buffer" or that "85 degrees is too high" ad infinitum. I'll stand by my rationale; an anaerobic niche, not aerobic, is the overriding concern in my opinion.

 

As I said, it's my opinion and don't let me deter you if you've settled on a course of action. Your nitrate readings will tell you if you've made the right choice, and that's all that counts. A properly set up tank will not have any detectable N cycle products, unless something goes wrong. And no, I've never had nitrates, even when my clownfish got caught in an intake and died while I was on vacation.

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I'd stick to the guidelines. The high surface area of highly porous rock means less of an anaerobic environment available for denitrifying bacteria. As a matter of fact, I'd use double the guidelines for highly porous rock.

 

Dr Ronald Shimek doesn't seem to agree: Live Rock as a Biological Filter: Hit or Myth

 

Here is a quote:

 

"Rock that is naturally porous and relatively light weight for its size would likely have more highly perforated internal regions and would function better in this regard."

 

Interesting article, to say the least! If anyone has anything more recent that contradicts his information, please share!

 

KC

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"Rock that is naturally porous and relatively light weight for its size would likely have more highly perforated internal regions and would function better in this regard."

 

That's what I would think. "Rocks" like many of mine that are just huge masses of feather duster tubes would have a ton of pretty deep dead spots inside them for anaerobic action.

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HecticDialectics
That's not too surprising. Online "research" will also tell you things like "there is an inverse relationship between calcium and carbonate hardness" or "solve low pH by adding buffer" or that "85 degrees is too high" ad infinitum. I'll stand by my rationale; an anaerobic niche, not aerobic, is the overriding concern in my opinion.

 

As I said, it's my opinion and don't let me deter you if you've settled on a course of action. Your nitrate readings will tell you if you've made the right choice, and that's all that counts. A properly set up tank will not have any detectable N cycle products, unless something goes wrong. And no, I've never had nitrates, even when my clownfish got caught in an intake and died while I was on vacation.

 

 

How do anaerobic bacteria and nitrates get to the center of a solid rock?

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formerly icyuodd/icyoud2
Not true at all. It's very possible to buy dead rock that is much higher quality than any live rock in a comparable, or even close, price range. The only down-side would be lack of diversity, which is completely avoided by properly seeding the tank, and a slightly slower stocking time, which isn't really a problem. Getting a nice coral hitchhiker is like getting struck by lightning unless you buy some TBS lr or something for a nice bit of change.

 

Cheaping out and filling the tank with crappy dead rock... solid blocks of fiji, lace rock, lava rock... will probably cost more in the long run, but there are CERTAINLY ways to get very nice rock economically. Not everyone wants to pay $10 a pound and go into debt for what may or may not be nice local rock.

comparing high quality dead rock to low quality live rock is kinda silly.

the idea is to get high quality live rock and not cheap out. :)

 

its not about coral hitchikers, its all about bacteria's,filter feeding animals on within the rock etc etc. none of which will be present on dead rock.

 

take 2 identical aquariums, fill one with live rock, the other with dead (both "high quality rock) and the live rock aquarium will cycle in a quarter of the time. the liverock will also be able to deal with your bioload alot quicker. add the diversity of life on/in the lr and theres no comparison.

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I think people are misunderstanding me. I am not saying that porous rock is not good. I am saying that the N cycle steps shouldn't be limited when setting up a tank. Many tanks I read about on this board do not give equal consideration to the microbial habitats which are the basis of LR "filtration". As a result many have nitrate problems becasue the focus is on aerobic, not anaerobic environments. Many concentrate on surface area and porosity of rock, neglect the anaerobic environment, and their lack of thought is proven by their nitrate readings. I am merely advising against this, one should not intentionally set up a chemical bottleneck immediately after ammonia and nitrite oxidation.

 

In nano tanks this is an even greater consideration because of the propensity for shallower sandbeds and less rock mass in general.

 

And I don't see anything contradictory in that article; Shimek doesn't address balancing the N cycle, but merely the N cycle in general terms.

 

How do anaerobic bacteria and nitrates get to the center of a solid rock?

 

"Rock" in the form of naturally formed LR is not solid.

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take 2 identical aquariums, fill one with live rock, the other with dead (both "high quality rock) and the live rock aquarium will cycle in a quarter of the time. the liverock will also be able to deal with your bioload alot quicker. add the diversity of life on/in the lr and theres no comparison.

 

Your argument seems to be based on getting a tank cycles as fast as possible. That's not a concern in my case, as I won't be stocking this with anything significant for quite a while.

 

What, in your opinion, does LR offer that properly seeded dead rock and patience can't duplicate?

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HecticDialectics
comparing high quality dead rock to low quality live rock is kinda silly.

the idea is to get high quality live rock and not cheap out. :)

 

its not about coral hitchikers, its all about bacteria's,filter feeding animals on within the rock etc etc. none of which will be present on dead rock.

 

take 2 identical aquariums, fill one with live rock, the other with dead (both "high quality rock) and the live rock aquarium will cycle in a quarter of the time. the liverock will also be able to deal with your bioload alot quicker. add the diversity of life on/in the lr and theres no comparison.

 

 

haha well nevermind then if that's what you base it on, then I agree. Dry rock does sacrifice a certain amount of life and hitchhikers. I'd take TBS LR and some sweet marshall and tonga rock covered in cool crap over even nice quality dry rock (If I had the money haha).

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"Rocks" like many of mine that are just huge masses of feather duster tubes would have a ton of pretty deep dead spots inside them for anaerobic action.

 

It's purely empirical; you won't know until you try it.

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And I don't see anything contradictory in that article; Shimek doesn't address balancing the N cycle, but merely the N cycle in general terms.

"Rock" in the form of naturally formed LR is not solid.

 

There is really only one contradiction, where you stated you would double the recommended amount for highly porous rock (implying that it is inferior in terms of filtration efficiency) while he states highly porous rock should be a more efficient filter.

 

I am NOT the type to pick one person (no matter what their "credentials" are) and accept their word as gospel, so please don't think I am discounting your opinion...sometimes hobbyists are "ahead of the curve" and the experts follow. ;)

 

But to address some other points, I've read the article carefully, several times. It seems to me that he is saying "dead rock" that has been "seeded" with live rock will never be as efficient as good live rock. In part of the article he states that flow into the interior of the rock is accomplished *not* by "external flow" (ie 10 huge powerheads turning a tank into a washing machine <VBG>) but by the action of small worms and "critters" inside the rock which are not present in "dead" rock. If I am understanding him correctly he says that bacteria and larger worms will "recolonize" the dead rock but the smaller worms that seem to be more critical for the interior flow won't.

 

I am wondering if this might go along with what Mr Anderson is saying, in that I could easily see nitrate problems resulting from what Dr Shimek refers to as "problem rock." At that point the relative porosity of the rock becomes irrelevant.

 

I guess the bottom line is that both Mr Anderson and Dr Shimek would agree that it isn't enough just to focus on the porosity of rock. :)

 

KC

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HecticDialectics
I think people are misunderstanding me. I am not saying that porous rock is not good. I am saying that the N cycle steps shouldn't be limited when setting up a tank. Many tanks I read about on this board do not give equal consideration to the microbial habitats which are the basis of LR "filtration". As a result many have nitrate problems becasue the focus is on aerobic, not anaerobic environments. Many concentrate on surface area and porosity of rock, neglect the anaerobic environment, and their lack of thought is proven by their nitrate readings. I am merely advising against this, one should not intentionally set up a chemical bottleneck immediately after ammonia and nitrite oxidation.

 

In nano tanks this is an even greater consideration because of the propensity for shallower sandbeds and less rock mass in general.

 

And I don't see anything contradictory in that article; Shimek doesn't address balancing the N cycle, but merely the N cycle in general terms.

"Rock" in the form of naturally formed LR is not solid.

 

Porosity is what helps reduce nitrates. Small deep holes don't have good water circulation and would be more oxygen deprived. Same way a nitrate reactor works... Porose and light rock would be able to absorb more water than a solid, dense rock deeper inside. I don't know the exact diffusion rate of water through porose rock, but I bet it's not fast enough to cycle oxygen.

 

I don't have any crappy big balls of dense LR on hand, but I bet if you smack it in half, the inside isn't wet.

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It seems to me that he is saying "dead rock" that has been "seeded" with live rock will never be as efficient as good live rock. In part of the article he states that flow into the interior of the rock is accomplished *not* by "external flow" (ie 10 huge powerheads turning a tank into a washing machine <VBG>) but by the action of small worms and "critters" inside the rock which are not present in "dead" rock. If I am understanding him correctly he says that bacteria and larger worms will "recolonize" the dead rock but the smaller worms that seem to be more critical for the interior flow won't.

 

Interesting. I was under the impression that a lot of the LR in the industry is "farmed" by dumping a bunch of dead coral in the ocean and then harvesting it at a later time. I would guess that this type of rock would suffer from the same problem?

 

An any case, I've already invested in the dry rock, and it's in my tank underwater right now, so I guess time will tell, ultimately. :)

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There is really only one contradiction, where you stated you would double the recommended amount for highly porous rock (implying that it is inferior in terms of filtration efficiency) while he states highly porous rock should be a more efficient filter.

 

I agree with him to a point; as long as there is sufficient denitrification then yes, porous rock is certainly more efficient than a solid slab of seeded stone.

 

However, along the continuum between solid stone and spongy rock, almost every LR specimen falls between. Porous is good, provided that oxygen gets depleted at some point in the rock, but water still flows. A mass of tubeworm shells sounds a little too porous to me to expect a slow enough flow for oxygen depletion. I'm not saying to not use it, but I might compensate with a thicker than usual sandbed, or something of the sort.

 

But I don't see the rock in question so please remember that I'm not telling anyone what to do, but that there are considerations when using rocks like this, or really thin Tonga branch.

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