How much Live Rock do you REALLY need?

[acroholic]

I personally think this is one of the grayest areas in reefkeeping. While I don't think it hurts to have more than you need, how much live rock do you really need in your system for effective biofiltration?

Is it absolutely necessary to stuff your sump full of it in addition to what you have in your display tanks?

I'll reference my two tank system that shares a common sump. I have a 300 gallon Marineland DD tank and a 150 gallon DD tank. I have about 200 lbs. of Totoka rock in my 300 and about 100 lbs. of Figi in my 150. These share a 75 gallon size sump (48" x 18" x 18") and a separate 15 gallon cheato refugium.

Outside of the 300 lbs. rock in the two tanks, I don't have any other live rock in the system and never have. My sump is bare except for whatever equipment is in it.

I have a medium-high medium density fish load, and I feed 2-3 times a day between frozen and dried foods. I do regular water changes, and also use a sulfur denitrator, GAC, and GFO, in addition to harvesting about 1/2 my cheato from the refugium about aver 3-4 weeks.

I have never had a nitrate spike and all parameters are very stable. And knock on wood, right now I have thriving coral colonies with excellent growth and color.

I've come to think that the practice of stockpiling a bunch extra live rock in the sump areas of the tank is something that just became common practice without much in the way of scientific support as whether or not it was actually necessary. The 300 lbs. of rock in my system seems to have no issue dealing with any nitrogenous waste produced by my fish.

Where did the 1.5-2 lbs. per gallon rule come from anyway? With open aquascapes, do people feel they need to shove the extra rock in the sump?

I think live rock has a lot more internal surface area for biofiltration than we give it credit for, and I would love to see any real scientific evidence that supports the 1.5-2 lbs. of live rock per gallon rule that seems to be the accepted standard.

I am operating just fine at a rate of about .67 lbs. per net gallon.

The above just my own opinions. Feel free to shoot it down or respond however.

Dave

 

[fish scales2]

Acroholic;573242 wrote:

and also use a sulfur denitrator, GAC, and GFO, in addition to harvesting about 1/2 my cheato from the refugium about aver 3-4 weeks.

This has everything to do with it!

I have seen many tanks run flawlessly with under a # of rock per gal. but they must be set up properly and slowly.

 

[jusney]

Lately I have been asking myself many questions (some of which have nothing to do with reef keeping) and have come to realize that many of the things we do were advocate by people who we respect and subsequently we have taken their opinions as gospel and made it a rule in our minds. I have personally known a person who kept a 180 FOWLR tank for the last 6 yrs with only about 100lbs of LR and what we would call an under sized air driven skimmer with more fish in that tank than I can count. As far as I am concerned, he has blatantly ignored all the rules that I follow. These are some of the reasons why I question some of the things we advocate as reef keeping laws here. Just my observation.

 

[acroholic]

I think the reef wall aquascaping practice has a lot to do with the 1.5-2 lbs per gallon rule that so many have followed. I did this myself until I switched to an open style with these two tanks, which, of course, needs much less LR than a reef wall.

 

[geno]

I'm glad you brought this up. While I may not have the expertise to address the amount of LR needed relative to its ability to filter the water -- I have over-done it a bit in my display tank -- thus reducing the viable area for my fish to swim. That may seem trivial compared to the reason we use LR -- but if less than 1.5 to 2.0 pounds per gallon does the job -- why clutter your system (and spend more $ than necessary)?

For me, discussions like this stretch the 'norm' and help create a new -- and possibly a new standard in the hobby.

 

[misu]

interesting, I wonder how seachem's matrix plays into this.

For my new 135 gal build I put about 70 lbs in the display, shoved another 60 lbs in the sump like you put it above then felt it's not enough and added 1 gallon of pond matrix and one gallon of regular matrix in media bags in different compartments of the sump.
Can't speak of any results yet since I'm going through the fallow period but I'll update this in a few months.

My other tank is more traditional at over 2 lbs/gal system

 

[mvm]

I agree that most people overdo it. I have a 70 cube, 25 gallon sump and 10 gallon fuge. I have a very open aquascape and what I would consider a heavy bio-load. I, like you, have a bare sump and no LR in the fuge. I have GFO and GAC as well. I probably only have about 50#, probably less LR in the tank:
Fish list:
Trio of Rhomboid wrasse
Onyx clown pair
leopard wrasse x 2
flametail blenny
Pink spotted goby
(thinking of adding a juvy harlequin tusk to complete the stock list)

 

[ivegotcrabs]

How much Live Rock do you REALLY need?

JUST ENOUGH TO FIT CORALS ON----LOL

 

[demifelix]

I used to have and holding tank with 3lbs of LR/gallon and I ran no skimmer and no other type of filtration. I do WC every 2 months and everything was fine, not perfect but fine (nitrate around 5-10 the whole time) and everything was thriving. I think the more equipment/filtration we use the less LR we really need.

 

[thbrewst]

Ayveq;573340 wrote: LOL, love this!


I wondered this too. Especially after we had the meeting with the speaker about aquascaping. I really don't like the current look of my tank and feel it is too packed with rock with not enough swimming room. After the meeting I did thin it out some and feel better about it visually, but was too afraid to remove more as I was afraid how it would affect the system. I honestly don't know how much live rock is in the tank as I bought it as an existing system.

I'm in a similar boat. I bought a previously set-up system from someone. I know how much LR they claimed there was, but how do I know for sure? I'm not planning to pull it all out and weight it. Based on his claim I am running ~1lb per gallon. System has not been set-up long enough to know if that is enough.

 

[misu]

Post some pics along with the tank sizes and we can give you some idea

 

[acroholic]

Forgot to mention that I also use a protein skimmer as well, of course.

 

[acroholic]

If you read a lot of the threads here about how big a sump should I have, you invariably get the answer "get the biggest one you can possibly fit into the space you have", or something similar. Not that a large sump or higher volume is bad and all, but I think there is a general push when giving advice to tell people that they always need "more" of whatever: live rock or sump size or actual system volume.

But you need to remember that if you are keeping your water changes to 10% a week for 100 or 400 or 1000 gallons, your expenses are going to be proportionately more for everything related to maintaining the water chemistry for that volume system, be it salt, electricity,
tap water to produce RO, RO Unit maintenance, additives, and especially equipment choices.

I had to upgrade my Calcium reactor from a GEO 618 to an 818, the cost of a unit sized to my system now is $700, $300 more than the 618 I just replaced.

Generally speaking, the higher your system volume the larger and more expensive any total system volume related equipment purchase is going to be. A system with 1000 gallons will use twice the salt, twice the RODI water, and twice the RODI source tap water of a 500 gallon system if you maintain the same percentage of water changes, outside of any additives, etc. That adds up to a lot of $ in the course of a year or two.

I remember a recent thread in which the poster was asking if a 40 gallon tank would be adequate for an under cabinet sump for a 175 gallon tank. Many people said no, well that is BS IMO, a 40 gallon tank is perfectly adequate, can contain an adequately sized skimmer, and contain any draindown that stops at the level of the overflows.

I had an MRC Reef Sump that measured 36 x 18 x 18 that was 50 gallons in capacity, and it serviced a 210 gallon and a 100 gallon reef perfectly and never overflowed from draindown.

What I am saying is that there are long term ramifications when we give advice to those relying on our experience. For a hobby as expensive as this, I think we are making it more expensive for some with the advice to go "as big as you can" or "as much water volume as you can".

In my case I keep the majority of my system volume concentrated in the Display Tanks themselves rather than behind or under the tanks in the equipment.

I think the "go bigger" and "more" mantra is well intended, but not always necessary, needed, or in the best interest of the person being given the advice, especially when you consider the expenses related to maintaining that higher volume of water or the cost of live rock.

 

[porpoiseaquatics]

IMO, you really can't use the #/gallon rule as different types of rock have different weight based on rock density. Branch doesn't weigh as much as table. Aquacultured generally weighs more than any natural live rock because it's largely limestone based and not very porous. The opposite could be said about man-made rock (the cement based rock that we make)...that is very light compared to the spacial volume that it takes up.

I personally am only running about 1 lb/gallon in tank/sump combination. So far, so good!

 

[ralph atl]

a few comments....................I always had as much live rock in my sump as possible to promote pods & bacteria growth........untill recently. I keep cheato down there and a couple of rocks, I find it easier to clean the detritus without it. That home depot wet/vac 5 gallon bucket is a great tool!

With so many aquarists using carbon dosing in one form or another (and you a sulfur denitrator), I agree Dave as the bacteria is multiplying and the nitrates are being removed by skimmer............


OK, so say you don't have an ULNS? no solid bio pellets, no fuel, no vodka, etc..........then you might need as much live rock as possible to rid your system from nitrates?

 

[acroholic]

mysterybox;573417 wrote: a few comments....................I always had as much live rock in my sump as possible to promote pods & bacteria growth........untill recently. I keep cheato down there and a couple of rocks, I find it easier to clean the detritus without it. That home depot wet/vac 5 gallon bucket is a great tool!

With so many aquarists using carbon dosing in one form or another (and you a sulfur denitrator), I agree Dave as the bacteria is multiplying and the nitrates are being removed by skimmer............


OK, so say you don't have an ULNS? no solid bio pellets, no fuel, no vodka, etc..........then you might need as much live rock as possible to rid your system from nitrates?

I don't think I qualify as having a ULNS system in a Zeo sense, and don't think I carbon dose, but you can tell me if a Sulfur denitrator the same as a carbon doser. As far as I know, a sulfur denitrator houses a very low flow, recirculating anoxic water column that has sulfur pellets in it that get colonized by bacteria that eat the nitrates, using the sulfur as fuel in the process and releasing nitrogen gas as nitrates are consumed. If that is the technical equivalent of carbon dosing via a different chemical pathway, let me know.

 

[ralph atl]

yup, same principle. kinda like bio-pellets or solid vodka dosing in a reactor.