Considering a "remote" deep sand bed

[davelin315]

I am thinking about adding a deep sand bed to one of my sumps by having my protein skimmer dump into a 32 gallon rubbermaid trash can that is placed into my sump. I was wondering what everyone's impressions of this are. It wouldn't truly be remote since it would be in my system instead of plumbed in somewhere else, but it would be separated from the rest of the system and would have clean water dumped into it, hence no accumulation of detritus. It would receive almost no light, only whatever happens to be in the room and what happens to spill over from the tank (almost none) and I would have nothing in there but the sand - no clean up crew, no sand critters unless they migrate in there themselves, nothing. Here's the question about this, I have 5 or 6 bags of sand left from when I set up my tank (40 lb. bags) of the oolitic sand and was trying to figure out if I should use this only or if I should add some silica sand below it as well (I have some playsand that I was contemplating using) or should I get some other sand, perhaps a large bag of reef grade sand (or try and join in the group buy before it's too late, if it's not already). I know that to be effective, a deep sand bed needs to be at least a 5-6" deep, so I'm trying to figure out how deep this one should be. I figure with the sand I have now the sand bed would be at least 1' deep, but I was thinking I probably should go deeper than that to be more effective, but I'm not sure. Also, the last time I added sand to my tank I didn't rinse it and the fine silt went everywhere. I'm wondering if this is good to keep in the deep sand bed or not and if it is, should I put it down, let it settle, and then add some rinsed sand on top to keep this stuff down? I'm worried about calcification of the sand and having it simply clump together and be useless. Anyone have any feedback on this? From my reading, it should not have life in it that produces waste and it should only get clean water, which is why the skimmer will dump into it directly. The footprint is just under 22" in diameter and the container will allow for up to about 25" depth.

[jamesbuf]

Back when I had my 180gal, I used a 42gal hexagon to run a remote RDSB. It was about 16-18" in depth. Over a two month period, I saw my nitrates drop from the 60-70s to below 10ppm. I made no other major changes to the system. I did very few water changes as well. If I had the room, I'd always run a RDSB. I like the idea of dumping your skimmer water into it too.

[lhcorals]

I am wanting to add a DSB when i do the add ons to my tank ( about another 220 gal's). How do you determine how big of a tank to use. I was thinking about a 20 Gal. high. Would this be big enough fo Approx. 500 Gal of total water volume? I not trying to steal your thread, just thought there might be a answer here.

 

Lynn

[davelin315]

Don't worry about it, Lynn, that's about the same thing that I'm asking anyway. I don't know what size is good and what size isn't.

[Origami]

I would wash the sand to remove the silt first before using it, Dave. One of the key principles here (as I understand it) is diffusion of water into an extended anaerobic sand layer to process and to reduce nitrates. I would be concerned that too much silt would impede diffusion (by clogging the bed), effectively narrowing your anaerobic zone and creating an anoxic zone where hydrogen sulfide pockets could begin to form. The effect would be worsened if the silt began to fuse to further limit diffusion.

 

Now, one of the benefits of a remote deep sand bed is that you can take it off line (for maintenance or whatever) without messing with your display. As long as your setup retains this feature (and it sounds like it does), you can consider it adequately "remoted."

 

Depth should be at least 5-6 inches, and can even be a foot or two. At some point, however, adding more depth would seem to be pointless as you're no longer building a deeper anaerobic zone but you're creating and deepening an anoxic zone. Where this point is, I can't tell you. It would, in part, seem influenced by the average size of your sand grains.

 

The composition of the sand should not make much difference at all. Silica sand should work as well as oolitic sand. The key factor here is the surface area that's available for bacterial colonization, not the composition of the sand. Silica has the added benefit of not fusing like aragonite does. (Aragonite is believed to fuse because of acids from bacteria lowering the pH in the immediate vicinity of the sand grains causing them to dissolve and to re-form.)

 

Light should not be an issue so long as you don't have algae and other organics growing on the surface of the sand bed.

 

Keeping detritus build-up down is important because you don't want to the RDSB to become a trap for decaying garbage and, therefore, a source for nutrients rather than a sink for them. Any way to accomplish that would be fine.

 

I run a DSB in the 180 display, but also have an RDSB of about 10-12 inches in a 20H tank using the aragonite sand from my old 90. (I had to do something with it....)

[basser9]

I HAVE RUN SAND IN ALL MY TANKS FOR THE LAST 15 YEARS MY PRESENT 150 HAS A 2/4INCH BED OF SOUTHDOWN....NITRATES STEADY AT .6........there were some great studies done a while back that showed that a 1 inch bed had up to 90 percent the nitrate lowering of a deep bed it was as low as 40 percent of a deep bed in other tanks.....put a inch in if it keeps nitrates below 1 then you have a bed running at 90 percent if not add more sand later.......you should always have cucumbers in your sand beds and some ceriths are a good idea.......sand is better in your main display/more volume/more diverseity...just better.........my 2 cents....i add aleast a inch in every square inch of my tank/sump/fragtanks and always have nitrates below 1......

[davelin315]

I have an average bed of about 3" or so, but it shifts around a lot and there are high and low spots. I have no anaerobic zone in my sand bed, with the possible exception of a few areas where there are large chunks of rock sitting on top of them, otherwise it's all exposed more or less to oxygen through critters or proximity to the surface.