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Sand bed

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RGibson

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Apr 4, 2004
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104
Anthony do you think a deep sand bed is still the right way to go for a reef tank? Hope you are doing fine and you need to stay home and finish that book.
 

Anthony Calfo

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Feb 19, 2004
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Location
Pennsylvania
Its not one way or the other my friend... deep sand beds work very well for some folks, and are not needed or do not work well for others.

The reasons for succeeding or failing with them are pretty clear... largely based on average aquarists lack of adequate water flow. My personal views on it are detailed at great length in the archives of WWM, RC and in the Reef Invertebrates book vol. 1

FWIW... I employ a very deep sand bed in most all of my systems and those that I have set up in the last fifteen years. I do have one sand bed that is now about nine years old and working like the others in my care - very satisfactory and as expected (nutrient source, denitrifying filter, tank buffer, etc)

Anthony
 

dnjan

alveopora
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Sep 9, 2003
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Could you elaborate a bit on "adequate water flow"? How do you avoid the sandstorm effect? Water flow higher in the tank, but less flow close to the bottom? And is the purpose of the water flow to remove detritus (through the overflow) rather than letting it settle?

thanks
 

Anthony Calfo

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Feb 19, 2004
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Location
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the problem with sand storms is not from excess water flow but from misapplied effluents. This occurs with the common application of a limited number of outlets (typically 4 or less) delivering all of the tanks water flow via powerheads, teed sump return, etc (regardless if they are harnessed by nifty devices like seaswirls [excellent] or not).

I address this issue at length in an article over at wetwebmedia.com called "Goodbye Powerheads..." [do a keyword search from the home page there to find it] :)

for adequate flow... it depends entirely on the species that you are keeping. As a general rule though, something around 20X turnover is a good start. Sps keepers can double this easily (see Paletta 2004, ref. 17-40X turnover averages)

The key is to have many converging effluents for the production of thorough random turbulent flow. Excessive laminar patterns are wat blow sand around terribly.

best regards,

Anthony :)
 

dnjan

alveopora
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Sep 9, 2003
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Thanks! I assume that the design you show in your article would result in significantly lower water velocities at the bottom of the tank than near the top, and that would probably help keep the sand in place as well. (I quite agree that misdirected, sustained laminar flow is what blows sand around).

I had a question about the detritus. With "enough" flow, are you trying to keep the detritus in suspension so it gets removed to the sump, or are you just trying to remove the products of detritus decomposition as they emerge from the sandbed?
 

Anthony Calfo

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Feb 19, 2004
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Location
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yes... quite correct. The goal in most any system is to keep solid matter/particles/detritus in suspension. Outside of a dedicated settling chamber, its a bad habit to allow any such detritus/matter to settle. Instead, keep it moving for filter feeders and filters to process it properly.

Anthony
 

dnjan

alveopora
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Sep 9, 2003
Messages
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Location
Seattle
You don't keep a Tang, do you? The water velocity necessary to keep those "detritus particles" suspended in the water column ...

Even urchin pellets are pretty big. And there are lots of them. I don't really think I would want those things blowing around in the water continually.
 

Anthony Calfo

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Feb 19, 2004
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1,183
Location
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as it is in the ocean... fecal pellets are a significant source of nutrition for countless life forms... there are studies on such "scatophagous" behaviors including calculated numbers of times fecal pellets are consumed containing copepods and how many times said microcrustaceans have to run through average digestive tracts before becoming adequately digested.

As for "projectiles" or the firmness of ANY fecal pellet in your system, ahhh... this is where you have thrown me. The integrity of fecal matter passed by aquatic lifeforms in the aqueous medium is... well... no integrity at all! Really, mate... they dissolve in seconds/minutes in the water column. Try picking one up (ewwwwww) :p Touch, net or siphon them and they dissolve readily/rapidly. Kept in suspension they can be processed by natural or man-made mechanisms. Left to settle in a poorly circulated tank and you get the common nuisance growths of pest organisms that so many people complain about.

Anthony
 

mojoreef

Reef Keeper
Joined
Jul 5, 2003
Messages
7,530
Location
Sumner
Hey Don I have a completely opposite system and yet it is what I strive for to. Its a great way to utilize waste for food.

Mike
 

dnjan

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Sep 9, 2003
Messages
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Location
Seattle
Anthony Calfo said:
(material deleted ...)

As for "projectiles" or the firmness of ANY fecal pellet in your system, ahhh... this is where you have thrown me. The integrity of fecal matter passed by aquatic lifeforms in the aqueous medium is... well... no integrity at all! Really, mate... they dissolve in seconds/minutes in the water column. Try picking one up (ewwwwww) :p Touch, net or siphon them and they dissolve readily/rapidly. Kept in suspension they can be processed by natural or man-made mechanisms. Left to settle in a poorly circulated tank and you get the common nuisance growths of pest organisms that so many people complain about.

Anthony
I guess I need to feed my tang more fiber! :)

Those urchin pellets, on the other hand, last a while.

I agree that too much detritus settling on the sand is a problem, but if nothing makes it to the sand, what do spaghetti worms, etc. eat?
 
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