How Deep Does My DSB Need To Be?

[FishDad2]

Anthony,

When I originally setup my new 225 gallon tank, I wanted to have a DSB as part of the setup, as it seemed they have a number of positive benefits...especially as regards denitrification in a reef tank. So, using the sand bed calculator, I figured out how much sand to buy and bought the recommended quantity of Nature's Ocean Samoa Pink #2 to build a ~4" bed.

Unfortunately, I ended up with between 2-3". As well, as I've now learned, the grain size of my chosen substrate is less than ideal...2.0 - 2.5 mm. In your article you describe it as falling in the "course grade sand" range, which isn't great for a DSB.

Having said that though, I wouldn't be surprised if the bags I acquired were mislabeled or Nature's Ocean doesn't do a great job of controlling the grain size, as only a couple of the bags seemed to have the larger grain size. A large percentage of what I got seems to be of a finer grain...not that there aren't larger pieces in there, but most of the bags seemed to be predominantly fine grains.

So, while the tank is in its relative infancy, only being in operation for ~3 months now, and I see many people reporting much higher nitrate concentrations than I (60 ppm vs. my 2.5 ppm), I am concerned that I may have created more of a nutrient sink than a DSB in the tank. And as you can guess, I'm looking for some guidance on how to remedy the situation.

Can or should I just add several inches of a fine grained sand atop the existing sand bed? If so, what grain size do you recommend and should I add it all at once or in stages? In short, how do you recommend going about increasing the depth and improving the overall makeup of the DSB?

As added detail to help you provide guidance:

1. Tank is 72" long by 24" wide and 30" deep
2. Flow is provided by a pair of Tunze Stream 6000's, Gen-X 70 as the sump circulation pump and Gen-X 40 on a closed loop spraybar at the base of the rock
3. Refugium has a DSB that's 6" deep with a 28" x 18" footprint...it's 60% Miracle Mud on one side and 40% ArgaMud on the other. I figured that, variety being the spice of life, it would be a good idea to have a varied substrate for the different critters that prefer one over the other.
4. Refugium is fed sump water via a MagDrive 9.5 pump

I've invested quite a few dollars and considerable time getting the tank setup, so I want to get things working properly before I start putting corals in there. As difficult as it is to restrain myself, I'll feel like dung if I put delicate life forms in there when I know conditions aren't what they should be and that I really don't have them under control.

Any help you can offer would be greatly appreciated.

Thanks,
Chris

[Anthony Calfo]

I would not add fine sand to the bed as it is... it will just settle in time. Likely be less than attractive too.

The larger grain size is not a death sentence either... although you will possibly need a lot more sand (than sugar fine) at depth to get the nitrate reduction you are looking for.

Why not go a while without adding it at this point to see if you even need it. Rob T did studies showing NNR at more shallow depths than most expected. Since the tank is filled already... it makes little difference if you do it today or next month or never... so long as the nitrates stay in the range you want.

So last of all... you just need to make sure(!) you are extremely mindful of the need for very dynamic water flow to keep solids in suspension to prevent this coarse bed from becoming a nutrient sink in time.

Frankly... I don't think its a big deal nor will it be difficult. Sand stir or even siphon periodically as needed to keep the bed fluid and not overburdened.

no worries... this can work.

And... its a beatiful grain/bed I suspect. Enjoy, but be diligent.

[kellymm7149]

3/4" starboard be will be perfect

[FishDad2]

Thanks Anthony...I'll let it go for a while and see what happens. If I ever need to add more depth though, perhaps I could go with the Samoa Pink #0, which has a grain size of 0.5 to 1.7 mm. Yeah, the smaller grains will settle over time, that's already happening, but at least it would be the same basic look and feel with a smaller grain size. And if I really want to go wild, I can sift it and only use the really small particles. Hopefully the bigger particles will breakdown and shrink over time. In the meantime, I can siphon and stir a bit to keep it as clean as possible.

As regards water movement, as I already have a pair of Tunze Stream's providing 1,850 gph of random flow each, as well as the Gen-X 70 (1,550) and Gen-X 40 (1,190), I think I'm as well covered as I can be in that regard...that's some 6,440 gph of rated circulation, or almost 29 times the tank volume. I don't know how much more I can realistically do at this point.

Let's see where it goes...thanks for the advice.

kellymm...what is "starboard" and what would I use it for?

[M.Maddox]

'Starboard' is like a cutting board surface for a bare bottom. That was a completely off topic and unhelpful remark by KellyMM7149.

DSB's are great, and there are several species of corals that cannot be kept long term without them.

[captbunzo]

I want MY next tank to have a starboard engine in it....

(Sorry, couldn't help myself)

[Anthony Calfo]

And we all return promptly back onto topic, riiiiiight?

posts re: the depth of DSB

Please

Start a starboard thread elsewhere if you like, folks.

(and the whip cracks... )

[FishDad2]

Anthony, now that we're back on topic, one of the other things I've been contemplating is creating are remote DSB as part of the system. I have an old 40 gallon tank that's collecting dust right now, so I've been considering using it as a second refugium or a truly deep DSB.

Assuming for now that nitrates become a bigger problem and I opt go with the DSB setup as a pure nitrate processing mechanism rather than another refugium, I have a few questions about how to maximize its effectiveness.

Should I just make the bed as deep as the tank will accommodate, leaving ~2-3" of water rapidly running over it or is there a recommended maximum depth of the bed which I shouldn't exceed?

What kind of sand (composition, size, etc.) should I use in a setup like this and can you point me to an inexpensive source for that sand? It'll take quite a bit of sand to fill that 40 gallon tank, and the typical aquarium sand tends to come at something of a premium, so...

I'm not going to rush into adding this to the system right away, as mentioned previously I'll wait and see how the tank behaves before taking action as you suggested. But since we're already on the topic, and it may eventually prove to be the prudent thing to do, I figure it's best to gain the knowledge now.

Thanks again,
Chris

[Anthony Calfo]

all good Chris

In fact... I recently stickied a thread on remote DSBs/buckets that I think will answer many of your questions about sand grains, depth, flow and installation in general:

http://archive.reefcentral.com/forum...hreadid=595109

Your remote unlit aquarium full of fine sand can work the same way, of course. Finer sands are better IMO... oolitic is better than sharp grains... and flow need only be enough to keep solids in suspension. Keep the remote DSB unlit for ease of maintenance too.

kindly,

Anthony

[FishDad2]

Ah...DSB in a bucket...sounds quite similar...I'll take a look at the 6 pages of posts.

Thanks again