substrate

Liz

Liz

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Mar 25, 2005
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Which is the best idea for a reef tank... deep substrate or hardly any substrate with frequent gravel-vacs? I had around 2-3" of crushed coral and aragonite in my FOWLR tank, but my nitrates were always testing high so I threw a bunch of it out and now have just enough to cover the bottom and I gravel-vac it and my nitrates are lower now. But now I want to take the tank mildly reef so I'm wondering if a deep substrate would be better.
 
if you have fish that dig through the substrate it will help alot. in a reef tank you will need about 1-2" crushed coral and 2-3" live sand. the live sand will have bacteria to break nitrates down better. anaerobic bacteria are key and without the deep substrate they dont work properly
 
Currently, there are 3 approaches to reef substrate:

1. Deep sand bed (DSB): this approach requires large amounts of fine sand (at least 4"). Overtime, it leads to anerobic denitrification with the addition of live rock and diversified sand stirring/cleanup crew of invertebrates. Pros: once established, as close to "maintenance free" as you can get + extremely stable parameters
Cons: initial expense with having to use so much sand; takes time (measured in months) to fully establish itself; not feasible in smaller tanks (lacking requisite sand volume/species diversity + may take up too much tank depth); anecdoctal reports of tank crashes after longterm use possibly due to phosphate buildup.

2. Bare bottom (BB): this method requires NO substrate, but removes organics before they have a chance to break-down into nitrate/phosphate in the first place. Requires very strong wet skimming and very high flow to suspend the organics in the water column before they can settle. Any detritus is syphoned out with regular water changes.
Pros: no sand to deal with or buy; good for SPS dominated tanks where utterly pristine water and high flow is required; attractive clean-looking tank
Cons: takes more work; fewer variety of creatures possible which require a sandbed such as conches and gobies; requires bigger pumps/skimmer; ugly weird-looking tank

3. Shallow sand-bed: the in between.
Pros: looks like what most people think an aquarium should look like.
Cons: not enough sand to really de-nitrify but enough to blow around if you put enough flow in to keep organics suspended in the water column.

Crush coral has fallen out of favour in reef husbandry given its tendency to trap detritus thereby becoming a nitrate factory which is a big no-no.
 
Please tell us how to change out crushed coral for sand without dismanteling everything & having sand & debris in the water column for days....I have over 80+ lbs of LR in my 75g already. Should I do 1 section at a time or add sand ON TOP of the coral & scoop the coral out as it filters to the top??????
 
68551 said:
Please tell us how to change out crushed coral for sand without dismanteling everything & having sand & debris in the water column for days....I have over 80+ lbs of LR in my 75g already. Should I do 1 section at a time or add sand ON TOP of the coral & scoop the coral out as it filters to the top??????
Click to expand...

When I took out my DSB, I did have to dismantle everything because what often happens with old substrates is that pockets of nitrogenous wastes can develop. Suddenly stirring around the substrate can release these pockets and cause nitrate and even ammonia spikes. This is bad, and this is why scooping out the crushed coral is probably not a good idea (besides creating a big mess).

However, if you still have a relatively "young" crushed coral bed that appears to be relatively clean, you can simply siphon it out over a period of several weeks with a piece of tubing that's large enough during water changes. This assumes that your rockwork is dispersed enough to allow you to get to most of the substrate.

If you've got a "rock wall" covering most of the tank bottom, changing the substrate without a complete tank breakdown will be very difficult.

Whatever you do, don't put in the sand before getting nearly all of the crushed coral out. You don't want two separate layers of substrate as the finer sand particles will actually migrate downwards under the crush coral over time. I found this out with my first SW tank when I cheaped out and bought cheap playsand for my bottom layer and the nicer, finer, more expensive stuff to put on top. Eventually all the coarse stuff ended up on top

Also two layers of different-sized particles is more likely create the aforementioned anoxic pockets within the substrate.
 
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Crown Royal said:
When I took out my DSB, I did have to dismantle everything because what often happens with old substrates is that pockets of nitrogenous wastes can develop. Suddenly stirring around the substrate can release these pockets and cause nitrate and even ammonia spikes. This is bad, and this is why scooping out the crushed coral is probably not a good idea (besides creating a big mess).

However, if you still have a relatively "young" crushed coral bed that appears to be relatively clean, you can simply siphon it out over a period of several weeks with a piece of tubing that's large enough during water changes. This assumes that your rockwork is dispersed enough to allow you to get to most of the substrate.

If you've got a "rock wall" covering most of the tank bottom, changing the substrate without a complete tank breakdown will be very difficult.

Whatever you do, don't put in the sand before getting nearly all of the crushed coral out. You don't want two separate layers of substrate as the finer sand particles will actually migrate downwards under the crush coral over time. I found this out with my first SW tank when I cheaped out and bought cheap playsand for my bottom layer and the nicer, finer, more expensive stuff to put on top. Eventually all the coarse stuff ended up on top

Also two layers of different-sized particles is more likely create the aforementioned anoxic pockets within the substrate.
Click to expand...



Ok, Now you've really got me crazy :sim:!!!!! First of all your post rang a bell with the "young coral bed" remark.....I never rinsed this coral when I inherited the tank & moved it....I thought rinsing would wash away the "good" bacteria.....So my YOUNG coral bed was actually someone elses OLD coral bed because the previous owner admitted that he NEVER did water changes & when I scooped it to move it & then put it back in the tank I REALLY stirred up the nitrates I bet :eek:!!!! :eek: !!!!
If thats true I'm lucky my nitrates aren't higher than the 100 I already have now.....

Also are the "anoxic" spots where the nitrates get eaten up???? If so, I'll mix the sand & coral now & be at "0" trates before I wake up tomorrow!!!!!! :dive2:
 
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Sorry for confusing you. I shouldn't be writing lengthy replies while trying to discipline a three year-old at the same time :dance2:

Anyway, now that I know that the crushed coral bed is indeed heavily polluted with crap, your only option is to get rid of it or it will continue to be a nitrate factory no matter what else you try to do.

The best way to do this without a complete breakdown is to siphon it out a portion at a time with each weekly water change so as not to disturb the trapped detritus too much.

But if you want to be absolutely sure that all sources of nitrate from the substrate have been removed from the tank, removing EVERYTHING from the tank and replacing the crushed coral with sand is what you must do.
 
Ok ....:thud: ...., I'm gonna bite the bullet.... How many pounds of sand do I need for a DSB??? The 75g tank is 48" long X 18" wide.....I'll pick a day to start when I've had lots of :coffee2: and do a little at each water change as you suggest & :fairy: Poof....I'll have fish that won't need gas masks anymore:dive2: .... :dive2: .... :dive2: !!!!!!!
 
Very good read Crown Royal!!! I'm ready to go buy some (detrovores?....spelling) I just wonder why they don't work in crushed coral too.....Sue
 
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