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tankgirl · 12-02-2003, 10:58 AM

Another comment by tdwyatt that's worrisome;
"If you want remote sand beds that work appropriately, you need water current slow enough to allow regenerative sediment settling."
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DSB's work fantastic on lagoonal soft coral type tanks. But the increasing realization that sps corals require high levels of water movement to thrive, is changing the way we run our tanks, and higher water movement levels present a problem for DSBs
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Also; a great post by adam

Any and all materials that aren't gassed off or aerosolized (trivial amounts except for carbon and nitrogen, and maybe a bit of sulfur) get incorporated into substrate, organics and organisms. These things must be exported. Period. for the rest of this post, I am referring to these materials

Nutrient cycling is important, but it is just that.... by definition, if it is cycled it doesn't ever leave. Choose your method... Skimming, Turf scrubbers, water changes, macro algae, whatever, but get rid of it. read on....

Populations of organisms in a DSB will rise and fall with available nutrients, but have upper population limits determined by factors other than food (space, primarily). They cannot infinitely absorbe this stuff and keep it incorporated. As they die for whatever reason, are replaced, and their nutrients are processed, where do they go? They go to DOM's, some get incorporated into sediments (a good bet since that is where they are!), etc.

Wherever they end up, they have to be removed. In a tank without a DSB, that means vacuuming, skimming, refugia and/or water changes in some combination. In the case of a DSB, that probably means periodic partial substrate change (probably in addition to skimming, refugia, etc).

I believe strongly that one of the reasons that DSB's are so successful for short periods of time and then rapidly decline is that they are very efficient at processing waste while the organisms in them are still growing in population toward their practical limit. When that limit is reached, and the popluation stabilizes, nutrient assimilation drops dramatically.

IMO, harvesting/exporting of animal mass is highly underrated as an export mechanism. Frequent trapping and harvesting of animals capable of rapid repopulation is a fantastic export mechanism. Bristle worms, several types of herbivorous snails and many sand bed critters are easy to harvest. Periodically removing and replacing part of a DSB will harvest a significant biomass as well as keep the infauna population constantly growing keeping nutrient assimilation high. It will also export any wastes incorporated into the sediments themselves.
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Another of the problems (as I understand it) is that with fluctuating nutrient levels, bacteria flourish and die. When they die, they release all the stuff locked up in their biomass - to fuel an algae explosion. Then as algae dies off, it refuels a new bacterial population increase - and so on in a vicious cycle.

12-02-2003, 10:58 AM	#15 (permalink)
tankgirl Reef Lobster Join Date: Nov 2003 Location: So. Ca Posts: 1,476 View Gallery Karma Komment	Another comment by tdwyatt that's worrisome; "If you want remote sand beds that work appropriately, you need water current slow enough to allow regenerative sediment settling." ----- DSB's work fantastic on lagoonal soft coral type tanks. But the increasing realization that sps corals require high levels of water movement to thrive, is changing the way we run our tanks, and higher water movement levels present a problem for DSBs ----- Also; a great post by adam Any and all materials that aren't gassed off or aerosolized (trivial amounts except for carbon and nitrogen, and maybe a bit of sulfur) get incorporated into substrate, organics and organisms. These things must be exported. Period. for the rest of this post, I am referring to these materials Nutrient cycling is important, but it is just that.... by definition, if it is cycled it doesn't ever leave. Choose your method... Skimming, Turf scrubbers, water changes, macro algae, whatever, but get rid of it. read on.... Populations of organisms in a DSB will rise and fall with available nutrients, but have upper population limits determined by factors other than food (space, primarily). They cannot infinitely absorbe this stuff and keep it incorporated. As they die for whatever reason, are replaced, and their nutrients are processed, where do they go? They go to DOM's, some get incorporated into sediments (a good bet since that is where they are!), etc. Wherever they end up, they have to be removed. In a tank without a DSB, that means vacuuming, skimming, refugia and/or water changes in some combination. In the case of a DSB, that probably means periodic partial substrate change (probably in addition to skimming, refugia, etc). I believe strongly that one of the reasons that DSB's are so successful for short periods of time and then rapidly decline is that they are very efficient at processing waste while the organisms in them are still growing in population toward their practical limit. When that limit is reached, and the popluation stabilizes, nutrient assimilation drops dramatically. IMO, harvesting/exporting of animal mass is highly underrated as an export mechanism. Frequent trapping and harvesting of animals capable of rapid repopulation is a fantastic export mechanism. Bristle worms, several types of herbivorous snails and many sand bed critters are easy to harvest. Periodically removing and replacing part of a DSB will harvest a significant biomass as well as keep the infauna population constantly growing keeping nutrient assimilation high. It will also export any wastes incorporated into the sediments themselves. ---------------- Another of the problems (as I understand it) is that with fluctuating nutrient levels, bacteria flourish and die. When they die, they release all the stuff locked up in their biomass - to fuel an algae explosion. Then as algae dies off, it refuels a new bacterial population increase - and so on in a vicious cycle.