Plenum or deep sand bed

[EddieKay]

I not sure if I should build a plenum to put in a new 75gal reef tank or just do a simple deep sand bed. It seems that if made incorrectly the plenum could be trouble(it seems that there many ways to make one).
Any thoughts
Also whats more popular

 

[Anonymous]

Properly maintained either would do well. Have you considered bare bottom or shallow sand bed? In any cace I would suggest plenty of current and heavy skimming.

 

[K9coral]

3" sandbed, minimal skimming, plenty of current...

 

[Anonymous]

Why 3 inches?

 

[K9coral]

No particular reason, lol, thats about the average depth in my "good" tank.

 

[Anonymous]

From what I recall a DSB needs to be in the 6" range to be effective. I think 3" is too deep or not deep enough.

 

[Anonymous]

Depends on what you mean by 'effective'! Denitro will occur in pretty much any sand depth.

 

[K9coral]

Well, I dont think that is the reason for my bryopsis and that is the only problem I have.

 

[PamRich]

I have a plenum with a 3" d protected sandbed above and 3" of unprotected sand above that. It has been set up like this for 10 years -- my tank is 30" d. I see no advantage to setting it up this way except that it made the tank shallower for me to work in. For asthetic reasons the sand brightens up the tank but My first tank was a bare bottom 125 gallon - I never had algae problems or diatomes or cynobacteria blooms --- I have experienced all of these with my current system. The BB is much easier to maintain.

 

[Unarce]

Depends on what you mean by 'effective'! Denitro will occur in pretty much any sand depth.

Now that's gospel!

Here are my sand bed templates :wink: :

If you were to set up a reef tank with high current, than there would be a lot of bare areas if you had a SB less than an inch high. 2-3 inches is the absolute best way to go. It would be incorrect to claim that a sand bed provides 'more capacity to nitrify and denitrify' simply because it's deeper.

"As much as 70 to 90 percent of the overall denitrification was located in the uppermost centimeter. The remainder was found at 1-3 cm depth"

-T.K. Anderson 1984 "Diurnal Variations of Nitrogen Cycling in Coastal, Marine Sediments."

"anaerobic habitat can be as small as 1mm, that aerobic and anaerobic bacteria essentially coexist, and that as little as 0.08mm distance is sufficient for nitrification and denitrification to take place simultaneously."

-Ecology and Evolution in Anoxic Worlds. Oxford University Press, Fenchel, T. and B.J. Finlay. 1995.

The misunderstanding is that areas with low levels of oxygen are a must for denitrification. Since we now know that aerobic and anaerobic bacteria exist together in the upper portion of the SB, than the heavy oxygen levels of our tanks would not be a factor. It's unlikely that denitrification will occur in the deep areas of a DSB, especially if nitrates never reach it in the first place.

I'd also like to point out that a deeper sand bed doesn't necesarily equate to more biodiversity of life. A shallow sand bed of numerous grain-size will create a number of different environments housing more life than a DSB.

Another misconception is that the smaller the grain-size, the more surface area there is for bacteria. This would certainly hold true if we assumed that every grain was a perfectly round sphere. But, take into account the rough edges, crevices, and porosity of larger grains, then it becomes quite comparable.

Like many, I like the pleasing aesthetics of fine sand (which makes up most of my shallow sand bed). But, having multi-grains with the larger pieces turning into miniature live rock themselves has certainly added to the sand bed's functionality as well as its appearance.

:wink:

 

[spsmike]

Well said reefnutz.

 

[spsmike]

Well said reefnutz.

 

[Unarce]

I'm useful on occasion :?

 

[Anonymous]

Rob Toonen did some studies that show sand beds and plenum systems perform pretty much identically, at lest within the parameters he looked at.

I'm currently in the process of siphoning out my sand though, and would go BB in the future.

 

[Unarce]

Were you having issues with you sand bed, Dan? Are you going to give starboards a try?

 

[Anonymous]

Well, I'm having some algae growth I could do without. And the sump is an area of slow flow with about 6 inches of fine sand. No way that can't be accumulating nutrients. And I want to be able to have more flow low in the main tank without a sandstorm.

Just barebottom for now, although the are enough ricordeas and zoos near the bottom that they will probably cover it well.

 

[Anonymous]

I prefer to use plant life like macros. In a refug sure, but thriving plant life make the actions of a sand bed irrelevant. And do a lot more than just consume nitrates. JMHO.

 

[Unarce]

Nuisance algae still seems to be plaguing a lot of aquarists. Good luck with that, Dan.

 

[starfish 1]

go bare bottom easy to keep clean and when the calcerious algae grows over is it looks good.I regret putting 1 1/2 inch sand in, now tank is to full to get it out with out causing havoc. Stacking your rocks is no problem if done with care.

 

[danmhippo]

Forget plenum, too much hassle.

I would go with 3" sand bed or bare bottom. Easier to clean and maintain.

Denitrification will start about 2" down. Sand bed of over 5" is over kill. I used to have a 12" sandbed in my refugium, and after a year, I see no life below the 6" depth. Another problem with sandbed too deep, IME, is any accidental disturbance of the sandbed, hydrogen sulfide that formed and trapped deep within the sanbed will be released.