[kissman]

What is the best substrate to use in a refugium and at what depth? 55g display and a 20g sump with a sopon to be 20g refugium.

[Samper]

I think a layer of miracle mud, possibly a thin layer of sand and some nice LR rubble works out great.

[kissman]

Not A Dsb?

[Samper]

Do you have a dsb in your main tank?

[Ninong]

Originally Posted by kissman

What is the best substrate to use in a refugium and at what depth?

I would choose a deep sand bed of at least 4" depth for a refugium.

[kissman]

what type of sand and crushed coral?

[Ninong]

Originally Posted by kissman

what type of sand and crushed coral?

I wouldn't use any crushed coral at all. I would choose a fine particle aragonite sand for a refugium. If you live near the coast, you should be able to find cheap aragonite sand at your local Home Depot's garden department under the brand names Oldcastle, Yardright or Southdown, followed by the phrase "Tropical Play Sand from the Caribbean." This is a seasonal item and may not be available at all stores during the winter but it is usually available at most Home Depot stores along the East Coast from Virginia to Massachusetts during the spring and summer.

Another option would be to purchase aragonite sand from your local LFS or online. ESV sells a very nice, fine particle oolitic aragonite sand: http://www.esvco.com/prod5.html That sand would be excellent either alone or mixed with the larger sugar-sized sand from Carib-Sea. Obviously these options would cost many times as much as the cheapy Southdown-type sands. The ESV product is the smallest particle size available anywhere. The good thing about the cheapy Southdown-type stuff is that it is a mixture of particle sizes with an average size that is just right for our purposes.

[Samper]

Ninong, what do you think about running a dsb in a refugium but barebottom in the display?

Someone a while back told me something negative about it although I can't remember exactly what was said.

[Ninong]

Originally Posted by Samper

Ninong, what do you think about running a dsb in a refugium but barebottom in the display?

There are any number of variations that will work. It all depends on what you want to accomplish with your refugium. The same can be said for the main display tank.

Most people run less flow through a refugium than they do through their main display tank. Therefore, it is possible to work with a finer particle sand in the refugium than you might be able to get away with in the main display tank if you intend running extremely strong flow through the main display tank.

If you choose to run extremely strong flow through your main display tank, you have two options:

(1) Bare bottom.

(2) A substrate that can tolerate extremely strong water currents.

Option number one is self-explanatory. Option number two could include a shallow substrate of crushed coral but that is not something that appeals to me. It could also mean that you choose a particle size that will not blow around in your tank with strong water movement. I refer you to Wayne Shang's reef system: Three inch deep sand beds in both the 718-gal main display tank and the refugium but they are not composed of fine particle aragonite. They are aragonite sands, just not all that fine.

My present 6" DSB in my 120-gal tank is Southdown sand. That sand is ideal for a DSB provided you do NOT intend to run extremely strong water currents in your tank. Some people are successfully running strong water current with a Southdown-type sand bed but this is not an easy feat. You can check out Kevinpo's setup for an example of a large tank with a fine particle DSB and strong water current. He attributes that to the large size of his tank. A fine particle DSB in a smallish tank (120 gallons or so) definitely limits your choices when it comes to water flow. This is nothing unexpected. In Dr. Rob Toonen's DSB articles, he tells you right upfront that a DSB is not recommended for an SPS-dominated tank with strong water movement.

There are many reasons for choosing a DSB in either your display tank or your refugium. One reason people choose a DSB over a bare-bottomed tank is that the DSB provides additional nitrogen reduction. Another possible reason for choosing a DSB would be for all the interesting life forms that inhabit it and for the diversity that adds to your system. It also allows you to keep animals that would be otherwise inappropriate without a sand bed.

If you are choosing a DSB for its ability to process waste (detritus) and produce food for the tank (larvae, etc.), then it is better to locate it in the display tank itself. Running a very large refugium with a DSB is fine but it is not as effective as running the DSB in the tank itself for several reasons.

How you choose to set up your system is entirely up to you. However, the purpose of a refugium is to provide refuge to animals and macroalgae that would otherwise be eaten in the main tank. That means that the refugium should not contain any predators of any kind -- no shrimp, no hermit crabs, certainly no fish, etc. A DSB in the refugium helps to produce extra food for the main tank provided that the refugium gravity feeds back into the main tank. Using the refugium as a place to grow macroalgae that can be periodically harvested to export nutrients was never part of the original concept but it is a useful practice thay many hobbyists employ as an added benefit. Using the refugium to grow macroalgae that can be used to feed herbivorous fish in your main tank is part of the original concept.

There are various different types of "deep sand beds." Most people think of the DSB in terms of the model popularized by Dr. Ron Shimek et al and if that is the model you are thinking of, then the size of your refugium is an important consideration. That type of a DSB is not self-sustaining unless it is greater than a certain minimum critical mass that Dr. Shimek says requires a tank larger than 25 gallons with a substrate depth of at least 4 inches. If that is the type of DSB you have in mind, then you can't do it in a small refugium (less than 25 gallons).

When you ask about deep sand beds, it can be confusing because there is more than one way to set up a deep sand bed. There is only one way to set one up if you are trying to duplicate the method recommended by Dr. Shimek but others do set them up differently. Inland Aquatics, for example, uses a mix of particle sizes that is entirely different from Shimek's approach and, in some cases, much deeper than Shimek's usual recommendations. One person who has written extensively on DSBs recommends a minimum of 3" (minimum!) while another recommends a minimum of 6"+. Shimek's usual recommendation is a minimum of 4" but I do remember him sanctioning a minimum of 3.5" once a few years ago when asked specifically by a member of RC if their 3.5" sand bed was viable.

[Samper]

The reason I ask is this:

I know the cpr refugium I'm using on my nano isn't approptiate to even consider putting sand in due to its size.

My 75 gallon will be run bare bottom though and have a 20 gallon refugium above it gravity fed down to the display. I figured if I could get a nice 6" fine particle sand going through it that it wouldn't be a problem at all and would actually add to the overall health and diversity of the system.
A 20 gallon is small but I'd like to set up a nice visible refugium and would love to have some of the diversity but if it's counterproductive to the bare bottom display then I'll figure something else out..

[Ninong]

Originally Posted by Samper

I know the cpr refugium I'm using on my nano isn't approptiate to even consider putting sand in due to its size.

It is certainly not too small "to even consider putting sand in due to its size" but it is too small to support the type of self-sustaining infaunal communities recommended by certain proponents of a certain type of deep sand bed. Those communities require a certain minimum amount of sand bed mass and, in particular, a certain minimum amount of "wall" space. That's not the same thing as saying that one should not consider putting sand in a CPR refugium.

One has to consider the purpose of the sand bed infauna and why certain minimum sizes are recommended. One of the "jobs" of the sand bed infauna in a fine particle, deep sand bed is to keep the sediments in motion. That is more important in a deep, fine particle sand bed than it would be in a less deep, less fine particle sand bed.

You do NOT require a minimum of 4" depth in your sand bed to achieve significant nitrogen processing benefits. You may require a minimum of 4" depth to achieve optimal nitrogen processing benefits and you may require a minimum of 4" depth to support the sort of diverse, self-replicating infaunal communities recommended as a vital component of such fine particle deep sand beds.

You can achieve a certain amount of denitrification with a 2" deep sand bed. We can even go in the other direction and say that some beneficial chemical processes require a depth of ~8" to become viable. Unless you have a very large, very tall aquarium, you will probably not give serious consideration to an 8" deep substrate but it is certainly an interesting option that others have employed successfully. I can think of one magnificent 650-gal Japanese reef aquarium that is running with a 10" deep sand bed composed entirely of what the owner calls "powder coral reef sand" that he collected himself. That tank has only been running for the past four or five years but his previous tank was running for 15 years without interruptions with a DSB, although one that was not as deep as his newer tank.

Denitrification is not the only reason for setting up a DSB. A deeper DSB will also process detritus. It would be better to avoid a protracted discussion of that aspect unless you are asking about how to properly set up a 4"+ fine particle DSB, which I don't believe is under consideration at the moment. Then we would have to discuss why you do not disturb the surface of a fine particle DSB.

If you have a small CPR hang-on refugium, it should have a minimum of 2"-3" of sand in the bottom. It will not crash, it will do just fine. It will not be the same as a DSB in the sense that you seem to be thinking of one.

My 75 gallon will be run bare bottom though and have a 20 gallon refugium above it gravity fed down to the display. I figured if I could get a nice 6" fine particle sand going through it that it wouldn't be a problem at all and would actually add to the overall health and diversity of the system.
A 20 gallon is small but I'd like to set up a nice visible refugium and would love to have some of the diversity but if it's counterproductive to the bare bottom display then I'll figure something else out..

It is NOT counterproductive to the bare bottom display.

It may or may not be viable with a 6" fine particle sand bed. It would certainly be viable with a 3" sand bed. These are not the same. The reason that you could run into problems with a 6" fine particle sand bed in a 20-gallon refugium have to do with the fact that a sand bed of that depth, composed of fine particle sand, needs to be turned to avoid clumping and other problems. It is turned by the infauna. The infauna need to be self-sustaining. In order for their populations to avoid crashing, they need a certain minimum amount of space -- both total volume and boundary space. The boundary space comes into play because their populations fall off near the walls of their confinement. The reason a 40-gal tank is better than a 20-gal tank for a functional fine particle DSB is twofold: It has more volume AND it has relatively more of that volume not in close proximity to a wall.

If I were setting up a substrate in a 20-gal refugium, I would probably go with a 2.5" sand bed. If I were setting up a substrate in a 40-gal (or larger) refugium, I would probably go with a 4"-5" fine particle DSB.

[jamestank]

Coincidentally, I am about to set up a refugium in the back of my 75 gallon Tenecor Simplicity Plus tank (simplicity plus means all the filtration is behind a false wall all within the same tank). The main tank has a 1" sand bed. Over the last 2 weeks I have removed the bioballs from the trickle filter. Unfortunately, the bioballs were spread over three separate chambers that made up the trickle filter. It is not practical for me to turn the three chambers into one chamber. I just bought some fully cured live rock rubble that I will distribute evenly among the three chambers that used to be the trickle filter. I will add more water to the tank so that what used to be the trickle chamber will be filled with water. I was not planning to use any substrate. Do you think this will work?

Any thoughts appreciated. Thanks.

Originally Posted by Ninong

It is certainly not too small "to even consider putting sand in due to its size" but it is too small to support the type of self-sustaining infaunal communities recommended by certain proponents of a certain type of deep sand bed. Those communities require a certain minimum amount of sand bed mass and, in particular, a certain minimum amount of "wall" space. That's not the same thing as saying that one should not consider putting sand in a CPR refugium.

One has to consider the purpose of the sand bed infauna and why certain minimum sizes are recommended. One of the "jobs" of the sand bed infauna in a fine particle, deep sand bed is to keep the sediments in motion. That is more important in a deep, fine particle sand bed than it would be in a less deep, less fine particle sand bed.

You do NOT require a minimum of 4" depth in your sand bed to achieve significant nitrogen processing benefits. You may require a minimum of 4" depth to achieve optimal nitrogen processing benefits and you may require a minimum of 4" depth to support the sort of diverse, self-replicating infaunal communities recommended as a vital component of such fine particle deep sand beds.

You can achieve a certain amount of denitrification with a 2" deep sand bed. We can even go in the other direction and say that some beneficial chemical processes require a depth of ~8" to become viable. Unless you have a very large, very tall aquarium, you will probably not give serious consideration to an 8" deep substrate but it is certainly an interesting option that others have employed successfully. I can think of one magnificent 650-gal Japanese reef aquarium that is running with a 10" deep sand bed composed entirely of what the owner calls "powder coral reef sand" that he collected himself. That tank has only been running for the past four or five years but his previous tank was running for 15 years without interruptions with a DSB, although one that was not as deep as his newer tank.

Denitrification is not the only reason for setting up a DSB. A deeper DSB will also process detritus. It would be better to avoid a protracted discussion of that aspect unless you are asking about how to properly set up a 4"+ fine particle DSB, which I don't believe is under consideration at the moment. Then we would have to discuss why you do not disturb the surface of a fine particle DSB.

If you have a small CPR hang-on refugium, it should have a minimum of 2"-3" of sand in the bottom. It will not crash, it will do just fine. It will not be the same as a DSB in the sense that you seem to be thinking of one.



It is NOT counterproductive to the bare bottom display.

It may or may not be viable with a 6" fine particle sand bed. It would certainly be viable with a 3" sand bed. These are not the same. The reason that you could run into problems with a 6" fine particle sand bed in a 20-gallon refugium have to do with the fact that a sand bed of that depth, composed of fine particle sand, needs to be turned to avoid clumping and other problems. It is turned by the infauna. The infauna need to be self-sustaining. In order for their populations to avoid crashing, they need a certain minimum amount of space -- both total volume and boundary space. The boundary space comes into play because their populations fall off near the walls of their confinement. The reason a 40-gal tank is better than a 20-gal tank for a functional fine particle DSB is twofold: It has more volume AND it has relatively more of that volume not in close proximity to a wall.

If I were setting up a substrate in a 20-gal refugium, I would probably go with a 2.5" sand bed. If I were setting up a substrate in a 40-gal (or larger) refugium, I would probably go with a 4"-5" fine particle DSB.

[Ninong]

Originally Posted by jamestank

Coincidentally, I am about to set up a refugium in the back of my 75 gallon Tenecor Simplicity Plus tank (simplicity plus means all the filtration is behind a false wall all within the same tank). The main tank has a 1" sand bed. Over the last 2 weeks I have removed the bioballs from the trickle filter. Unfortunately, the bioballs were spread over three separate chambers that made up the trickle filter. It is not practical for me to turn the three chambers into one chamber. I just bought some fully cured live rock rubble that I will distribute evenly among the three chambers that used to be the trickle filter. I will add more water to the tank so that what used to be the trickle chamber will be filled with water. I was not planning to use any substrate. Do you think this will work?

Any thoughts appreciated. Thanks.

I'm familiar with the Tenecor Simplicity Plus tanks. I would probably do something similar to what you are considering. I would place a few smaller pieces of live rock (not necessarily too small) into those compartments to act as additional filtration. You don't want this to be very small pieces that could settle down into a sort of compacted substrate. You might also keep a little Gracilaria algae in there if it receives some light. You can feed that to any tangs or rabbitfishes but it won't last in the main display tank because they will eat it all within a matter of hours.

[middlemark]

Ninong - I like your advice, a lot.

For the `above tank 20g fuge' ... IMO that's about the only way I'd add a refugium to my BB tank. In-sump I found to be quite a detritus trap - and that's the one thing I would pay attention to in any BB with refugium tank.

I know in my BB tank, with heavy flow - particulate is constantly in the water ... going through the system. A low-flow place in the sump I found to be a settling chamber [what I use it for now] ... and provided you can avoid pulling from a detritus-heavy area - I like the above-tank idea as IMO it probably should have a little less `settling' than some other places in the system.

IMO, having the main place where detritus settles being a 'fuge/DSB is asking that to handle a lot of load - maybe more than it would be ideal to do [esp if a smaller sandbed area]. But, an above-tank refugium not located in a `heavy settling area' would probably thrive a little more and not become a home for debris [difficult to remove in a sand bed].

My apologies if this is too much a curveball - but figured I would try to follow Ninong's good advice with my own idiosyncratic take on it.

[jamestank]

Thanks - do you think I should put floss pads over the chambers that now serve as the refugium? I had floss pads on top when it was just bio-balls but I'm not sure how I should handle that situation now. There does appear to be a lot of particles always floating in the water. I think the cause of this may be insufficient water flow so I'm also thinking of adding a powerhead to move things around some more.

The more research I do, the more I wish I would have not have rushed into the Simplicity Plus!

Originally Posted by Ninong

I'm familiar with the Tenecor Simplicity Plus tanks. I would probably do something similar to what you are considering. I would place a few smaller pieces of live rock (not necessarily too small) into those compartments to act as additional filtration. You don't want this to be very small pieces that could settle down into a sort of compacted substrate. You might also keep a little Gracilaria algae in there if it receives some light. You can feed that to any tangs or rabbitfishes but it won't last in the main display tank because they will eat it all within a matter of hours.

[Ninong]

I wouldn't put floss into the chambers with the live rock. The live rock itself performs the same function -- biological filtration.

Whether you should use any form of mechanical filtration depends on your setup and what equipment you are running. It might be necessary to run some sort of filter pad (or filter sock) to trap particulate matter but a good protein skimmer might take care of that by itself. Any sort of filter pad should be cleaned frequently, sometimes as often as two or three times a week.

[marxsman]

just a friendly tip. If you add sand into a tank take a strong magnet and run it through the sand many times. You will be amazed how much magnetic stuff come out. It removes all the metals that should not be in a reef tank. I founf d that out the hard way.