husbandry tips with 215g and shallow sand bed...

[scottjj]

I am setting up a new Oceanic 215 RR (72x29x24). It is drilled with 1" drains and 3/4" returns. I plan to use a 55g sump, a 20g fuge, a Mag 9.5 on each return and a Mag 18 on a closed loop. The LR is about 100lbs Fiji and 70lbs of Marshall. I will use an ETSS protein skimmer pushed by a Mag 7. The lighting is all PC with a 48" Satellite and a 60" Orbit Extreme (about 660w total). I plan on keeping a mix of relatively easy corals as I do not plan on getting any MH lighting. Livestock plans are for all non-predators such as a Sailfin, a powder blue, a rabbitfish, 1 dwarf angel, 1 larger angel, mated clowns and something schooling, Anthias or similar. I also have 8 various serpent stars and 8 fire shrimp and cleaners from my current tank.

I have been reading as much as possible about the BB/DSB debate. I do not want to further the debate, as I am 90% sure that I do not want to go DSB (and I don't like the looks of a BB). In short, what are the challenges to be faced with a large tank and a shallow sand bed of 3/4" to 1 " ?
With this depth, should I use crushed coral ? sugar sand ? in-between ?
If I use a DSB in the fuge, will I gain back some of the de-nitrifying affects lost by not using sand in main tank ?
I was thinking that 170lbs of LR would enable me to maintain a healthy system with weekly 20g water changes.....agree ? Should I add or reduce flow with the closed loop ?

[tdwyatt]

With primarily fishes and Octocorals, your tank is actually ideal for a DSB biotope.

Lighting, coral selections, fish selections (herbivores) and substrates so far already tip your system towards such a biotope. Depending on houw you set such a system up, your overall plan would benefit from such a decision early on.

jm2cw

[drw94]

I have read recently in a Marine Reef Magazine that SSB are excellent and providemost of the same de-nitrifying effects of a DSB. But also remember that LV also has enormous de-nitrifying capabilities. With a SSB they recommend gradual replacement overtime. You should siphon a little sand when doing a water change, and when the sand gets low you replace it with more sand. You should check out the web site oregonreeg.com. This guy has a really succesfull tank and he has a shallow SSB operated under similar conditions. Also check out Marine Fish and Reef Magazine, Volumn 6 2004. It goes into great detail about all SB. The thing to remember is that with any sand bed, they act as dump for unwanted things, such as phosphates. This is a good thing as long as you replace it from time to time. In the ocean there are creatures that consume phophate and other unwanted stuff, so in a tank you have to remove the sand before it gets saturated and replace with new. The timeline for this is still being debated. For myself a siphon a little sand during everywater change and replace it when it gets low.
Goodluck.....keep us posted on the progress

[tdwyatt]

Originally Posted by drw94

I have read recently in a Marine Reef Magazine that SSB are excellent and providemost of the same de-nitrifying effects of a DSB. But also remember that LV also has enormous denitrifying capabilities...

well, not really.

I won't repeat the debate on DSB's here, just check out the thread(s) in the think tank. The advantage of using DSB's relates to the anaerobic threshold reached in the DEPTH of a sand bed as bacteria exhaust the interstitial pore water oxygen while consuming organic carbon for heterotrophic metabolism. Over time, a gradient is established, and bacterial speciation will begin to select those organisms that can utilize other elements besides oxygen to act as the electron donors during the breakdown of carbon bonds for energy. Some organisms do not even depend on carbon for their source of energy for phosphorylation (ADP--->ATP). Although many of these organisms can be facultative in their choice of oxygen for this purpose, others are not, and depend solely on whatever electron donor their metabolism is based on. Other organisms can enzymatically produce oxygen from other sources, either by preferentially removing oxygen atoms from their molecular partners or by using the entire molecule as an electron receptor and converting it to a different oxidative state. Those organisms that we are most interested in are those organisms that can take nitrate and strip off the oxygen atoms for use in their catabolism of organic carbon, or create new molecules from nitrate to form metabolic intermediates that are capable of further metabolism to molecular nitrogen gas by other bacterial species. It is this combination of processes that make the strong suit of DSB's that shallow sand beds cannot achieve Ideally mineralization will occur in close proximity to the anaerobic denitrification processes, and although Live Rock does this quite efficiently, DSB's can do this with greater volume and load capacity, depending on the particle size of the substrate in question, the biological carbon load, phosphate and nitrate loads, and interstitial perfusion rates affecting the oxygen gradient.

The biggest drawback of DSB's is that they will, over time, become saturated at somewhere between 20 to 40% adsorption of phosphate. In addition, end-detrital compounds and biomass (bacterial) produced will sink much of the phosphate in dead bacterial biomass. This biomass ultimately will end up in depths of the sand bed where recycling by consumption of the bacterial biomass is either difficult or impossible by bioassimilators due to the same oxygen gradient that makes the DSB work. If we had some higher organisms that could consume this sand and poop nice little pellets of phosphate-laden-totally-insoluble-easily-exported critter poop, the entire issue could be laid to rest and all of us would be trading in the commerce of these critters.

If we had some higher organisms that could consume this sand and poop nice little pellets of phosphate-laden-totally-insoluble-easily-exported critter poop, the entire issue could be laid to rest and all of us would be trading in the commerce of these critters.

Unfortunately this is not the case. Bacteria always win in the competition for end detrital phosphates.

This is not to say that we cannot control and manage our sand beds so that they have relatively long lives and when the phosphate saturation is reached that we find a happy equilibrium. We DO NOT have to remove the sandbeds, and in fact, doing so is counterproductive to good sandbed management unless you're replacing it each time with new live sand infused with organisms intended to replace and broaden lost benthic diversity. My OPINION on the subject is that with appropriate sand bed construction so that good circulation can always occur (little if any rock resting on the sand bed surface), controlling large pulses of carbon, good water quality, adequate lighting (yes, this IS a big deal), providing for detrital control and export prior to the production of nascent orthophosphates, and additional export mechanisms to capture whatever portion possible of those phosphates that do appear; that it is possible to extend the lifespan of sandbeds for periods exceeding 5 to 8 years (both personal experience and those of a few aquarists with whom I communicate). The biggest issue with DSB's is that there is no clear and concise methodology outside those promoted by a few folks that see the sandbed and an endless eternal mulch pile, and although the function of the sandbed is much like a terrestrial mulch pile, we are much more limited in our ability to just sink nutrients here, as the entire water column in closed systems is an extension of the top few layers of the sand bed's interstitial water chemistry.

whew... too much caffeine this afternoon.

[tabwyo]

I'd side with Tdwyatt, the man knows his stuff.

[tdwyatt]

OK, enough with the PM's.

The difference between areobic and anaerobic respiration is the ability to utilize oxygen vs little or no oxygen to "burn" carbon for energy. Some bacteria are able to carry out anaerobic respiration in which an inorganic molecule other than oxygen (O2) is the final electron receptor. For example, some bacteria known as sulfate reducers can transfer electrons to sulfate (SO4--) reducing it to H2S. We sometimes see these in the substrate of aquaria and are harmless so long as the substrate is not disturbed. The presence of H2S in the water column is self-limiting in that it is being produced in areas of low to zero oxygen tensiion. Other bacteria, called nitrate reducers, can transfer electrons to nitrate (NO3-) reducing it to nitrite (NO2-). Other nitrate reducing bacteria can reduce nitrate even further to nitrous oxide (NO) or nitrogen gas (N2). These are the species we are interested in.

Like aerobic respiration, anaerobic respiration involves glycolysis, a transition reaction, the citric acid cycle, and an electron transport chain. The total energy yield per glucose oxidized via anaerobic catabolism is less than with aerobic respiration with a theoretical maximum yield of 36 ATP or so. Depending on spp, anaerobic respiration may be as low as 2 molecules ATP per molecule glucose.

[scottjj]

Thanks all...I had forgotten about the oregonreef website...I like what he is doing....vaccuming during water changes and adding back substrate every couple of months or so.......both he and Tom have it together...