What's the diff in setting up sandbeds??

[goodreef]

For those interested in setting up a sandbed, we are often faced with 3 basic questions ...

What sand grain size to use?
What depth to use?
To use a Plenum or not?

Read this, and it might change how you feel about the above ... it certainly changed my views of things!!!

Feature Article: An Experimental Comparison of Sandbed and Plenum-Based Systems. Part 1: Controlled lab dosing experiments
http://www.advancedaquarist.com/2005/6/aafeature

Feature Article: An Experimental Comparison of Sandbed and Plenum-Based Systems: Part 2: Live Animal Experiments
http://www.advancedaquarist.com/2005/7/aafeature

Please comment on article. Thanks.

[goodreef]

Some interesting quotes:

"Putting aside all the rhetoric and opinions, our experiment shows that the presence of a plenum has no measurable benefits over simply depositing the same sediments directly on the bottom of the aquarium (at least over the few months that we tested)."

"In terms of processing nitrogenous wastes from aquarium inhabitants (specifically ammonia, nitrite and nitrate), none of the experimental treatments (plenum vs. sandbed; deep vs shallow; coarse vs. fine) appeared to have a significant advantage "

"The interaction of the depth and particle size of the sediment bed made the greatest difference to the overall performance of the system throughout these experiments, and the presence or absence of a plenum beneath those sediments showed no significant effect in any experimental parameter measured "

"The significant differences among the experimental treatments were almost entirely in the buffering capacity of the sediments rather than the biological breakdown of nitrogenous waste products. The largest differences among the treatments were seen in the final concentration of phosphate: coarse sediment treatments had roughly 17 times the final concentration of aquaria in fine particle treatments! "

"Overall, deep coarse sediments without a plenum had the lowest death rate in the experiment (1.0 ¡Ó 0.58 animals replaced), while shallow coarse sediments above a plenum had the highest overall death rate (4.0 ¡Ó 1.53) in the experiment. Shallow coarse sediments without a plenum (2.67 ¡Ó 0.88) and shallow fine sediments with (2.67 ¡Ó 0.33) or without (2.33 ¡Ó 1.20) a plenum were all on the higher end of the death rates recording in the experiment as well (Fig. 10). These higher mortality sediment combinations are closest in design to those of the Berlin (NPSC) and Miracle Mud (NPSF) systems (Figure 10)."

"To our surprise, the majority of the nutrient processing capacity appears to be explained quite simply by microbial processes. These experiments show no evidence that the presence or absence of live animals and sediment infauna have a measurable effect on the nutrient processing capacity of sediments "

"The simple prediction based on sandbed depth would be that deeper and finer sediments should always have reduced oxygen penetration and therefore increased nitrate processing capacity (Toonen, 2000a; b; Shimek, 2001; Delbeek, Sprung, In press). Therefore, it is hard to explain why deep, coarse (27.41 mg / L ¡Ó 6.89 SE) and shallow, fine (20.42 mg / L ¡Ó 6.89 SE) sediments have the highest average final nitrate concentration, while shallow, coarse (12.08 mg / L ¡Ó 6.89 SE) and deep, fine (0.67 mg / L ¡Ó 6.89 SE) sediments consistently had the lowest final nitrate concentrations. "

[goodreef]

So, what would you choose if :

1. Your sand bed is in your MAIN TANK.
2. You need high water flow for SPS corals.

(Assuming results are the same with or without plenum.)

Deep Coarse = Lowest death rate, BUT highest phosphate. Mid nitrate processing capacity.

Deep Fine = 2nd Lowest death rate, 2nd lowest phosphate, highest nitrate processing capacity, BUT may not be suitable for high water flow.

Shallow Coarse = High phosphate, high nitrate processing capacity, BUT highest death rate.

Shallow Fine = Lowest phosphate, BUT high death rate, may not be suitable for high water flow. Mid nitrate processing capacity.