How deep must sand bed be?

HendrikKotze

Bristleworm
Joined
22 Feb 2008
Posts
66
Reaction score
0
Location
Centurion
I have started filling up my 500 liter tank this weekend with RO water and it is about 3/4 now. I want to scape the sand bed, but have some questions.
I have filled it up with 40 kg (1 to 3 mm) and 20 kg (6 mm) crushed coral. It is apparently not the best, by my LFS did not have aragonite.
Currently the fine coral is at the bottom and the coarse coral are on top and it is about 50 mm deep.
How deep should it be and should I mix it?
I would like to finish it before the tank is full.

Thanks,
Hendrik
 

Alfie

Hawkfish
Joined
5 Oct 2007
Posts
1,607
Reaction score
14
Location
Cape Town
IMO you can make it as thick as you want to. Did you put the sand in after the water?

I ask because it helps to get all the air out so that their are no air pockets.
 

Quinton

Smarty-pants Newbie
Joined
5 Feb 2008
Posts
451
Reaction score
7
Location
San Francisco Bay Area, California
You should toss the crushed coral - it traps detritus badly. Get something much finer (ideally aragonite, but you know that already ;-). Shallow sand bed should be approx 15mm deep (or 100mm+ for a deep sand bed, but you probably don't want that). Anything in between can be problematic. Can give you further details if you like, but not right now ;-)
 

sihaya

Cardinal
Joined
6 May 2007
Posts
1,494
Reaction score
38
Location
USA
I wish I still had the link to the great in-depth article Dr. Toonen wrote on all this... but basically, the sand bed needs to be at least 3 to 4 inches. At the same time, much deeper than 6 to 7in and you don't get much added benefit.
 

LikesFish

Blenny
Joined
20 Jul 2007
Posts
939
Reaction score
15
Location
Canada
I'd swap the crushed coral and finer sand around - have the finer sand on top. This way you will reach your anaerobic zone sooner...

But yes it is better to have all fine sand. You mention 1 - 3mm, and 6mm. An ideal DSB should have about 75% particles of 0.125mm in size - way smaller than yours.

And the sand should be oolitic - i.e. rounded, so that it does not hurt your microfauna.
 

sihaya

Cardinal
Joined
6 May 2007
Posts
1,494
Reaction score
38
Location
USA
I'd swap the crushed coral and finer sand around - have the finer sand on top. This way you will reach your anaerobic zone sooner...

But yes it is better to have all fine sand. You mention 1 - 3mm, and 6mm. An ideal DSB should have about 75% particles of 0.125mm in size - way smaller than yours.

And the sand should be oolitic - i.e. rounded, so that it does not hurt your microfauna.
Ditto. This is also discussed in depth in Toonen's article. Finer sand results in higher bacteria counts. Though it does make it more difficult to prevent sand clouds, dunes, etc. One way to deal with all that is to just use a remote refugium (which is always an excellent addition to any system anyway).
 

Quinton

Smarty-pants Newbie
Joined
5 Feb 2008
Posts
451
Reaction score
7
Location
San Francisco Bay Area, California
I wish I still had the link to the great in-depth article Dr. Toonen wrote on all this... but basically, the sand bed needs to be at least 3 to 4 inches. At the same time, much deeper than 6 to 7in and you don't get much added benefit.
Here's the Toonen article you're (probably) looking for:

Advanced Aquarist's Online Magazine - Feature Article: An Experimental Comparison of Sandbed and Plenum-Based Systems. Part 1: Controlled lab dosing experiments

But I think we're getting confused here (at least I am). The original posting was asking about a (shallow) sand bed in the display tank (as opposed to a deep sand bed in a sump/refugium). Correct me if I'm wrong. Shallow sand beds are almost exclusively aerobic in their action. Deep sand beds incorporate significant anaerobic bacterial action. There's a lot of literature out there on the production of toxic hydrogen sulphide (H2S) by anaerobic bacteria in deep sand beds. I don't have the article handy now, but I read a very convincing study recently showing that aerobic sand beds should not be much deeper than 15mm to minimize anaerobic action. Deep sand beds should be at least 100-150 mm deep to achieve the full denitrifying effect of anaerobic bactierlal action, and mitigate the risks of toxic hydrogen sulphide expulsion from the sand bed.
 

Warr7207

Moorish Idol
Joined
28 Dec 2007
Posts
12,781
Reaction score
31
Location
JHB
Interesting Article

The one statement that stood out for me:

"We urge hobbyists to develop a good 'BS' detector that will allow you to question information presented to you without any experimental evidence to support it."
 

Alfie

Hawkfish
Joined
5 Oct 2007
Posts
1,607
Reaction score
14
Location
Cape Town
Hendrik, is this not your sandbed for the display tank you are refereing to and not DSB as such?
 

HendrikKotze

Bristleworm
Joined
22 Feb 2008
Posts
66
Reaction score
0
Location
Centurion
Hendrik, is this not your sandbed for the display tank you are refereing to and not DSB as such?
This is for the sand bed in my display tank. Currently about 50 mm deep. I do not have space in the sump for the DSB. I have filled the sump with rock and cermaic rings, which I have also read is not 100% correct?
 

HendrikKotze

Bristleworm
Joined
22 Feb 2008
Posts
66
Reaction score
0
Location
Centurion
Thanks. I will read the article tonight.
What is I removed the coarse coral and added aragonite?
 

Matt

Wrasse
Joined
5 Jan 2008
Posts
1,976
Reaction score
41
Location
JHB
toss the ceramic rings, put the rock in your display and made a DSB in your sump.
 

mandarinman

Achilles Tang
Joined
18 Oct 2007
Posts
6,377
Reaction score
70
Location
capetown,durbanville
matt that is an alright opinion, i have got my dsb in my tank, cos it works for me, fine media, cos i have experienced larger grain causing higher phosphates, in my naon which i am closing down soon. i prefer having an ecosystem instead of a display tank mentality( both are fine) just think a dsb the size of your tank , lekker, works for me and just think a couple of neon faced gobies munching through the sand the whole day(will make sure the liverock os secure). it would be an option to have a dsb in your sump but if you do not(emphasized)have space it is fine to have one in your tank. ps dont talk about dead spots( if you are tempted) cause in a dsb there is a huge one across the bottom of the whole thing(imo).
 

HendrikKotze

Bristleworm
Joined
22 Feb 2008
Posts
66
Reaction score
0
Location
Centurion
matt that is an alright opinion, i have got my dsb in my tank, cos it works for me, fine media, cos i have experienced larger grain causing higher phosphates, in my naon which i am closing down soon. i prefer having an ecosystem instead of a display tank mentality( both are fine) just think a dsb the size of your tank , lekker, works for me and just think a couple of neon faced gobies munching through the sand the whole day(will make sure the liverock os secure). it would be an option to have a dsb in your sump but if you do not(emphasized)have space it is fine to have one in your tank. ps dont talk about dead spots( if you are tempted) cause in a dsb there is a huge one across the bottom of the whole thing(imo).
I have a sump, but it is not configured for a DSB - it has 2 small chambers between the protein skimmer and the pump chamber. How fine is the media in you tank?
I am thinking of removing the coarse coral and replacing it with aragonite before I add the live rock?
 

Quinton

Smarty-pants Newbie
Joined
5 Feb 2008
Posts
451
Reaction score
7
Location
San Francisco Bay Area, California
Yeah - replace the coarse coral with fine aragonite, irrespective of whether you decide to go deep or shallow. The data on coarse vs fine is pretty clear - go fine!

Q
 

mandarinman

Achilles Tang
Joined
18 Oct 2007
Posts
6,377
Reaction score
70
Location
capetown,durbanville
good reading quinton, i agree, imo the fine sand prevents detritis collecting and decomposing between large sand particles
 

sunburst

Foxface
Joined
8 May 2007
Posts
2,420
Reaction score
25
Location
Durban
Agree. Fine on top..... While the bed is still young its still cool to swop. But do not leave it to long
 

Top