Deep Sand Bed Removal debate

[Funkyskunk]

Hi guys why are having a debate on South African reef keeping site about the removal of a DSB, now my way of thinking is to remove the sand bed slowly and in stages as not to adjust the environment of the corals to quickly and to allow the corals to adjust to the new parameters slowly.

They are arguing to rather do it all in one go, now I agree that the tank is does not have a huge amount of stock, and that it would be possible to do this all in one go.

However I am curious to the correct method of removing a established deep sand bed?

Any advise or opinion would be greatly appreciated.

Thanks

Christiaan

[TJcop]

I did it all in one go. It was much easier to do that way. I emptied all the water, corals, rock, fish into holding tubs. Then I used a shop-vac and sucked out all the sand. I put in my starboard, some PVC racks to help with circulation and then all the livestock. I haven't looked back yet!!!
Good luck!

[wasp]

If it is an old sand bed, and you remove it in stages, what you are in fact doing is exposing new layers of crud to your tank water all the time. Far better to get it over with in one hit.

[mesocosm]

Greetings All !

However I am curious to the correct method of removing a established deep sand bed? ... my way of thinking is to remove the sand bed slowly and in stages as not to adjust the environment of the corals to quickly and to allow the corals to adjust to the new parameters slowly.

Visualize a deep sand bed as a vertical column of biologically and biochemically inter-connected layers. Different layers have different associated water chemistry, different meiofauna populations (bacteria living on the surface of the particles of the layer), and, to a lesser extent, different infauna populations (organisms inhabiting the spaces between the particles of the layer).

Biologically and biochemically inter-connected ... this is critical. The disruption of one layer effects the functional "behavior" of all of the other layers.

There are two primary problems associated with the "peeling away" of layers as part of a "in stages" removal process. Problem #1 is that as you remove an upper layer, the biochemical processing taking place in lower/deeper layers is disrupted. This can result in incomplete oxidation, incomplete reduction, and diminished sequestration of nasty chemical intermediaries ... PO4, NO2, H2S, SO2, SO4 ... to name but a few. In other words, there is the potential for the accumulation of undesirable ... and potentially lethal "re-release of ... reactants and products. Problem #2 is that deep sand beds need to be ... well ... "deep" in order to function properly. Every time you remove a layer, you are diminishing the physical space that DSBs require to process "wastes" effectively ... which takes you right back to problem #1.

Disruption of the functioning of a DSB can be catastrophic ... the release of potentially lethal chemical intermediaries and metabolites can occur very rapidly. Such "crashes" are almost never slow enough to give the aquarist time to react. While the slow removal ... ~ 1/4" every 24 hours ... of DSB layers has some appeal ... for the very reasons cited ... the potential for rapid "meltdown" is a risk that I would have a hard time accepting.

I guess that puts me in the "all at once" camp ...

"Total" removal of a DSB in "one shot" minimizes the release of chemical "nasties" into the water column. But some release is inevitable during the removal process. Disruption to the water chemistry that coral specimens are acclimated to can be minimized by siphoning out and storing 75% of the systems water BEFORE removal procedures begin. After the DSB is completely removed and the tank rinsed, the "old" water, plus 25% "new" water should minimize the disruption to coral specimens. Assuming the absence of a large fish bioload, the presence of an established biological filtration component ... like live rock ... and care not to overfeed the system during the first few weeks after DSB removal, I would think that the negative impact on the coral specimens would be minimal.

JMO ... HTH

[Funkyskunk]

Thanks Guys,

Great to have you experts, to help us out here in SA. Thx for that Gary, quoted it on the SA site. So well put as always!!!

Christiaan