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Christopher Marks

2/23/04 - Substrates

This week's topic is:

 

Substrates

 

When setting up a new reef aquarium, one thing we all have to consider is our substrate. What type of substrate will be used? What grade of substrate (course or fine)? How deep will it be in the tank?

 

Common options are aragonite, silica sand, black sand, and crushed coral.

 

There are many different methods and ideas around sand beds. Some of these are deep sand beds, plenums, shallow sand beds, or no substrate at all.

 

In this weeks discussion, share your experiences with different substrates and sand bed methods. What worked and what didn't? Also ask any questions you have about sand beds or types of substrates.

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i vote for well turned over, well used- DSB .....easily confused with the DSB that sits there, and crashes.... sure it has dangerous potential.. but it also comes with some pretty nice tank health points that you don't get anywhere else... cheaply

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We have set up our new 20g with crushed coral and about 5 pounds of sugar sized live sand for seeding. The coral makes up the first four inches, and the sand and coral mixed is the top 2 inches. We have sand sifters and disturb the top 1/2" of everything every week. We have no plenum. So far everything is great! The cycle went very quick, and have lots of pods and worms. We have duplicated this setup in the new 10g as well. It is cycling quite fast as well. (only been up for 6 days and already showing nitrites and amonia at 0 and nitrates at 5) We also put the live rock in first and poured the substrate in around it. This has created stability, and helped to seed the CC with the orgs in the LR. We feel this setup is on the right path. The tank is crystal clean and smells good. *sniff sniff*

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Personally, I prefer bare bottom. Easy to clean, doesn't trap detritus, and doesn't allow for pockets of toxic substances.

 

I know some people think it's unattractive, but with a little patience, you can have the bottom glass covered with mushrooms or green star polyps, if you'd rather.

 

All that said, in my latest tank I went with a very thin layer of crushed coral, for reasons involving a significant other's asthetic ideals. I can still very easily sift through it and stir it up, to get detritus out, but it doesn't blow around under the high currents in the tank, like most finer substrates would.

 

A lot of people claim that sandbeds are required for good denitrification, but the fact is that the live rock alone is more than sufficient. And it does provide the anoxic regions where nitrate processing occurs. A DSB does provide more, and much more anaerobic regions (important mostly for processing of unwanted minerals), but they come with significant risk and an expiration date. But with a little maintenance effort, a substrate-less tank is just as healthy, and much more consistent in performance.

 

Or, at least, that's my opinion on it all.

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I prefer a sand bed of aragonite. I've heard that larger crushed coral trapped detritus and was harmful to benthic fauna (ie; sand critters) due to their sharp shapes. However, I did add some "live sand" from someone else's established tank, which contained CC, and I bought LS from Dr Mac, which also looked very CC like, but the rest of the sand is Caribsea "oolitic" sand. I also have 150 lbs of Southdown awaiting a larger tank.

 

Actually, I enjoy the fact that stuff lives in the sand, I like my tank to be an ecosystem...that is the part that fascinates me. Admittedly, it makes it hard to keep powerheads aimed low, and if a powerhead loses it's tenous suction cup hold on the tank glass...watch out!

 

I keep a relatively deep DSB in my sump, just in case it makes a difference.

 

V

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Just a comment on the crushed coral harming sandbed fauna:

 

I've never noticed crushed coral to be sharp, but it is definitely large and pokey (for lack of a better word). My rule of thumb is that animals who ingest sand (sea cukes, jawfish, etc.) should probably be avoided. But most others are fine. Just my half inch of CC is teeming with breeding mini-stars and bristle worms, and quite a few nassarius snails.

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i have tried a few diffent sizes of substrate in the bottom of tanks over the years and my current tank is using ultra fine sugar araganite which is a beautiful soft texture that also gives the benifits of a DSB in 1.5 inchs deep

it is so fine that detritus stays on top for easy cleaning or eating :) it can also blow thru the gills of fish without harm

 

but I have seen a black version that looked super sweet too!

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mixed black and white bio-active aragonite sand in my 10g. about 1-1/2" on top of 1" of crushed coral.

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I like southdown, preferably 1/2in or less. Nice and clean.

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I have modified plenums in both of my 20g. reef tanks. What I did was use penn-plax UGF's which I capped off. I drilled out one of the caps and inserted some black 1/4" hose more commonly used for ornamental pond pumps. There's about three feet of the black hose snaked under each UGF plate, with small drill holes about 2" apart drilled into the hose itself. About 2" of hose sticks up through the cap above the UGF plate, which i've capped off with a black plastic cap and tucked into the sandbed along the back side of the tank.

 

This "underhose" creates something a little new to the hobby, called a super plenum. The big controversey over plenums is that they may (keyword: may) become fouled over time, or if the sandbed is too deep, could potentially turn anoxic. With the hose modification, I can actually draw off water from underneath the plenum plate in the future if i'm worried about compound build up. By slowly drawing off any scumwater from under the plate, I can slowly drain out the water with an artists syringe, or even a modified powerhead, any time I think things have gone wrong in the plenum. It's like having a plenum with an insurance policy.

 

However, the jury is still out on plenums and DSB's. Just as many people have them as do not, and there's nothing wrong with doing your tank setup as a "berlin" (sand free) or a "monaco" (plenum/DSB ).

 

I followed Jean Jauberts methods for setting up my plenums right out of John H. Tullock's book "Natural Reef Aquariums." It's a fantastic book for beginner and advanced reefer alike. Here's what John & Dr. Jaubert recommend for plenum tanks:

 

Create the plenum plate out of a UGF plate or eggcrate. Cap off the UGF with the hole caps if need be. Place the plate in the bottom of the aquarium and cover it with a sheet of fiberglass or nylon windowscreening (non-metal) from a hardware store. You'll have to pre-cut the screen with sharp scissors as it comes in rolls like christmas paper.

 

Then, add a fine layer of non-calcarious/non-silica sand, such as quartzite sand or pool filter sand, to about 1.5-2" of uniform depth. This fine sand layer is your dentrification zone. The rationale behind a non calcarious sand for this layer is to avoid concretion problems commonly associated with silica and aragonite based sand. Experienced reef keepers have experienced this, when silica begins to stick to the sand and it tends to clump up like scoopable cat litter. You can break apart these clumps pretty easily by hand or with a pair of reef tongs, but it's going to be impossible to do this in a DSB. So, he advocates using a fine grade of sand as outlined above for this layer, to avoid concretion in the dentrification zone. Also, since aragonitic sand will dissolve over time, you don't want your bottom sand layer to be one you have to replace. You can replace the top sand layers every six months to a year or so by just adding new sand on top, but not the bottom layer.

 

After you've poured and leveled your first layer of sand, cover it with another layer of windowscreening. Then, add an additional 2-3" layer of aragonitic sand, such as caribsea seafloor special grade or araga-max. This layer should be variably rubbly/chunky with medium sized sand grains.

 

That's it. That's all there is to it. If the sand is too deep, it could turn anoxic and start to produce hydrogen sulphide gas. This is easily spotted as the tank will begin to stink like rotten eggs. You can remove 1" of surface sand and fix it. If the sand is too shallow, it might never develop a dentrification zone (low oxygen zone) and your tank will consistently show nitrates. The fix is to add a little more sand to the top layers.

 

Plenums take time to break in, just like cycling a new tank, before nitrate levels will fall. The more friable the upper surface layers are, the better, so a healthy worm/pod population really helps. Sand stirrers, such as nerite snails, white brittlestars and gobies will also help keep the sand from compacting as well.

 

I took my substrate one step further and seeded it with GARF Grunge+ (www.garf.org), which is a mix of miracle mud, live sand and reef rock rubble. It's chock full of life and will rapidly seed aragonite sand. I love this stuff. I have all kinds of shrimps, pods, tubeworms, spaghetti worms and even teeny brittlestars crawling around in my sand thanks to Garf. Looking at the upper aragonite layer reminds me of looking at an ant farm as a kid, except that now i'm watching pods and little baby cleaner shrimps (they pink up early!) crawl through the substrate. Ooh, what is that.. what's that thing... where's my magnifying glass gone?

 

Is it the right way? Who knows. It's working very well for my tanks. All nitrogenous readings are zero, pH fluxuates a little between the light/dark cycle between 8.3 and 8.0 (I blame my DOC algaes) in one of my tanks because it has no refugium (the other does, and the pH is more stable). The alkalinity of the tanks run about 11 dKH and the calcium levels are approx 420 ppm.

 

I like the natural reef appearance and the benefits of NNR (natural nitrate reduction) the DSB/Plenum provides, as well as a further buffer for the pH and the reintroduction of calcium/strontium/magnesium as the aragonite layer dissolves slowly over time.

 

But that's just me! :);)

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look, have to put my 2 centson the plenum issue. after much research and talking- they appear to " reduce the sediment volume that is available for the bacteria. " as quoted by Dr. By Ronald L. Shimek [see article link below]

 

 

in terms of DSB i think he is the bomb. he is the basis of how i set my current one up, and i shopped around [looked at GARF, which has some REALLY good advice in places] , but have found that the plenum trend seems to be more operated on urban legend than auctual data.

 

 

 

http://www.rshimek.com/reef/sediment.htm

 

this article does the best job of sand beds.. covereing better than anyhting short of buying a book and reading in regards to DSB, and composite- why to avoid crushed coral, etc.. why not to buy sand shifting stars for deeper sandbeds.. etc.

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Being a newb I'm trying to learn. No experience with sand or crushed coral in marine tanks. Have used crushed coral in a fw tank w ug filter with no trouble as long as I kept it clean.

 

Used dolomite gravel w ug filter with airlift or with powerhead in fo marine tank. It compacts to a rock hard layer if not stirred up regularly. Collects lots of crud too, and must be vacuumed often.

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Live Aragonite here, from Florida/Bahamas, slightly pinkish and bright white, very nice, not too big, but not as fine as sugar sand. I am planning on adding some sugar sand in another few weeks or more arag to create a DSB, right now it goes from 1 inch to 3 in the back.

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