Cycling: Live Rock vs. Base Rock

[Aegeon]

I'm currently in the middle of a 25g cube build (here), and have some questions about cycling using dry base rock. I've searched around and read quite a bit, but I'm still a little fuzzy about how it should go. Sorry about the "wall o' text"....

 

From what I understand of cycling, it goes about like this (in layman's terms): Something adds new or additional bio-load to the aquarium system (decaying matter on new live rock, adding a new fish/coral/invert, etc). Bacteria in the system must proliferate in order to compensate with the higher load and re-establish a balance, which takes time to accomplish and can be monitored via water parameter testing. When all parameters return to 0 (or nearly so), it is assumed that that balance has been re-established.

 

In a new tank started with all live rock, I understand how this works. The system is essentially sterile until live rock is added. The live rock adds a massive (in relation to total system volume) new bio-load to the formerly sterile system in the form of dieoff/decay, hitchhikers, bacteria, etc. The cycle progresses as dead matter decays and is consumed, bacteria proliferates, etc until eventually balance is acheived and the intial cycling is "complete". After completion, enough organisms exist within the system to sufficiently cope with each stage of the process of converting organic wastes to nitrogen, based on the current bio-load. Upping the load on the system (by adding new livestock, etc) causes this process to repeat, though most likely on a much smaller scale than the initial massive bio-loading.

 

However, when starting a new system using dry rock, the system is still essentially sterile after the rock is added. Adding a small amount of "seed" live rock from a well-established system provides the starting bio-load, but assuming the live rock is well established, decay should be minimal and the rock should already have quite a bit of beneficial bacteria within it. Additionally, the amount of "seed" rock is very small compared to starting the same system using all live rock. I would assume, therefore, that the ammonia spike and subsequent cycle would be relatively short, as the one piece of live rock is the only bio-load in the relatively large (in terms of total volume) system. Once enough bacteria exist to keep the load of that one piece of live rock stable, the cycle should end, correct?

 

If this is correct, then upon completing their cycles, both systems above should be in equilibrium internally, biologically speaking. However, the system started entirely with live rock now has a much larger bio-load (and much more bacteria handling each stage of the ammonia-nitrogen cycle) than the the one started with just a small amount of live rock. If additional bio-load is added (a new small fish, for example), the system with all live rock should be better equipped to handle the change, as the additional load of the fish is smaller in comparison to the existing load in that system than if the same fish were added to the dry rock system.

 

So, am I correct in thinking:

 

1. Starting a system will all live rock should result in a large initial cycle, but additional bio-load should be adjusted for more quickly.

 

2. Starting a system with all base rock (plus a live rock "seed") should result in a smaller initial cycle, but additional bio-load should be adjusted for more slowly.

 

Any thoughts?

[TinyGiant]

go with live rock IMO. you'll get fun little critters and a more stable system quicker.

 

i always look around to see if there is anyone in the area with a large tank that i could get the water and rock from. Usually from someone tearing down a tank on craigslist or within the forums. if you can grab water from an established tank and rock.. you are pretty much going to have a turn key system

 

but i think getting live rock is not only better but far more interesting. also i find alot of time that base rock lacks shape and character. you can usually find better shapes and such with live rock.

[DRLOVEtoreef]

I am going to disagree ... going with live rock opens you up to all kinds of risk ... critters you don't want, bryopsis, rock full of phosphates etc ... you can take live rock and "cook" it for 6-8 weeks to get rid of a lot of the nutrient build up, but, that is a pain.

 

dry rock is going to be much cheaper, you can choose your shapes and sizes much easier, don't have to worry about bad algae or pests, and, lets you work on the aquascaping at a much easier pace. Plus, you can add 1-2 small pieces of clean live rock (i would keep it in a bin for 3-4 weeks with saltwater and a power head and keep it dark ... ala cooking) to remove any crap. after a few months, you won't know the diference ...

 

here is an example ... i started this tank about 9-10 months ago ... here it is on the first day

 

here is a picture from a few days ago

 

i did have some algae i have dealt with, but, that came in on frags mainly ... i paid $1 to $2 a pound for the rock ... cured it in some ro water for a few weeks and then added it.

 

it does take longer to get your system stable, but, in the long run, I would rather sacrifice those extra 4-6 weeks vs. dealing with pests or nutrient build up

[cheryl jordan]

Nice example of how dry rock colors up, it's cheaper and you cut way down on the heart ache and frustation of pest.

 

Nice system BTW

[DRLOVEtoreef]

thanks - if i was better with a camera, i would show more

[seabass]

So, am I correct in thinking:

 

1. Starting a system will all live rock should result in a large initial cycle, but additional bio-load should be adjusted for more quickly.

 

2. Starting a system with all base rock (plus a live rock "seed") should result in a smaller initial cycle, but additional bio-load should be adjusted for more slowly.

Given a similar ratio of rock to water, you are still making some assumptions. However, your reasoning is basically correct. Some variables include how 'cured' the live rock is in each scenario, and how much dried organic matter is on the dry rock.

 

Most of us assume that a tank that primarily starts with dry rock won't support as large of an initial bio-load. However, as you add to the bio-load and the fauna spreads to the base rock (and sand), both tanks should eventually support similar bio-loads.

Note: I'm ignoring the benefit of the diverse fauna that comes on quality live rock, as well as the potential pests that it can also contain.

[lakshwadeep]

I think most of your assumptions are correct.

 

One thing to note is that most nitrifying bacteria are very quick to grow, so even a tank with a majority of previously dry rock should eventually be able to hand livestock additions similar to a system with all "original" live rock. Also, a large cycle will mainly occur based on whether the rock is cured and its transportation method.

 

Another point is that it can be very hard to tell how high the initial ammonia spike will be with unfamiliar rock, even if it is all live rock. And, over time, it is possible that after the ammonia spike, the bacterial populations will decrease due to ammonia not being produced in such an abundant amount. I guess it would be useful to know how long the increased bacteria populations due to an all-live-rock cycle would last. Another question would be that the bacteria likely have predators of their own, and their may be other organisms competing for ammonia and it's products (mainly algae blooms). These interactions and food chains are probably what makes finding a definitive answer very murky.

 

One difference to note about previously base rock and initially live rock is that there is often a long succession of organisms besides bacteria that colonize the rock. It often mirrors what happens on the glass in a new tank (first microalgae then later on other things like sponges, coralline algae, worms, pods, etc.).

 

I think that after a short period (maybe even a few weeks) an initially base rock system will be able to handle livestock additions at the same level as an all live rock system. It may be that for a base rock system, microalgae help out with the added influx of bioload a lot as they have more areas to proliferate (coralline algae and other more "delicate" algae usually limit the available surface area for colonization).

[Aegeon]

Thanks for the great replies! As usual, very informative.

 

I'm asking all this because I'd like to start my tank out using primarily base rock for several reasons (control of pests, easier aquascaping, cost, etc). The plan for my 25gal is to start with ~25 lbs of dry rock from BRS. Their Eco Rox product looks pretty nice, seems to be cost effective, doesn't damage existing reefs, etc. I'll then attempt to get 5-6 lbs of established live rock from a local source. I'm hoping to be able to keep the live rock submerged & heated for nearly the entire transfer between tanks.

 

I'm hoping by going this route, the initial cycle will be very fast, depending upon the quality of the live rock I'm able to get. My plan is to monitor for that cycle to end, then start stocking by adding a single small fish, most likely a Firefish or small Ocellaris Clown. When that fish hits the water (along with it's food), the bio-load in the system should go up. Since there will not be much of a load in the tank prior to the fish with only 5 lbs of live rock, I'll monitor water parameters and do water changes as necessary until the tank stabilizes again. Rinse and repeat, adding another single fish/invert or small coral frag group each time the tank stabilizes for a few weeks.

 

I figure this method should let me get something in the tank sooner, but may take longer to get the tank fully stocked, which I'm ok with. Also, as has been mentioned, as bacteria increases with each "mini-cycle" following a livestock addition, the dryrock system's capacity to handle an increasing bio-load should eventually catch up to that of a full live rock system. (My wife has stated she's tired of looking at "the big glass box" in the living room, and that she'll be better with my time/money investment once she "actually sees a fish" )

 

It'll be interesting to see how it goes. Thanks again for the insight, everyone!

[lakshwadeep]

I'm actually doing this right now, with less than a pound of live rock and roughly 15+ pounds of dry rock from my previous setups. After a week, there were no ammonia and nitrites, and nitrates were also fairly low. There was a some significant hair algae growth, but they are very pale and likely caused by nutrients present in the dry rock (which was left outside for months/years).

 

I did deviate from my normally scheduled stocking after a month when I got two small Trimma gobies, and they're doing fine after a week. I do know that these additions will be problematic with the feedings probably increasing algae growth rates, but so far there hasn't been any spikes on the tests or even algae blooms.

 

One thing I have noticed is that there are some small red "fungus" growths scattered throughout the tank that are probably sponges.