Substrate question for the experts

[dakota9]

My substrate is probably something most people have never seen, as I think reefers stopped using it a long time ago. It's made up of tiny clam shells. Well, actually some sort of bi-valve mollusk, not crushed shells but like those tiny little shells that wash up on florida beaches in great numbers. I've got like 2 1/2 to 3 inches of this shell on the bottom of my tank, I want to add a layer of carib sea sand on top of the exsisting substrate, what do you guys think? I've read that a DSB should be less than one inch or greater than 3, and I think I'm like in the "mid-zone.

Dakota

 

[xyzpdq0121]

Ahhhh someone from florida must have told you how to set up your tank back in the day. The only people I have known to use the shells you are talking about are from flordia but it was popular about 10 years ago because it was cheap to collect and easy to come by. Not the best substrate in the world though, hence why stuff that corse is not used much anymore!

Well, mid zone is bad so yes if you are going to go DSB then go over 3" and since you are using "large grain" substrate, I would reconsider a DSB anyways and keep it to under 1" or go well over with the new added sand to about 4-4 1/2". But if you are dead set on keeping what you got in there, here is what <u>I</u> would do: Siphon out your bed REALLY well to remove anything that might be stuck inbetween the shells in in the bi-valves. Then add 1/4" of carib sea about ever 2 weeks untill you get the depth you want. Do not mix the two layers. Utilize the sand to keep crap out of the shells. The is a method we used to use way back in the day to get the (limited) benifits of a course sand bed with the filtering of a finer grain sand bed. All be it, there is a reason that this is not done much any more, it did not work too well! My other advice (although, if you are going to go trough the trouble just replace your sand bed!) is that you can remove the rock and place some screen material down between the two levels of different substrates to keep them from mixing and to keep critters out of the shells. Think pleanium type theory. But again, if you are going through all that, then just replace you sand bed with something better.

 

[FutureInterest]

I'm no expert by any means, but I'll impart what knowledge I have gleaned... The key to determining the necessary depth for a sand bed is the size of the particles that make up the substrate. The smaller the particles, the less depth you need to create an anaerobic zone for denitrification. As such, using the small shells, although attractive, have two drawbacks. First, you'll find that crushed coral and shell based substrate tend to trap detritius and particulate matter more than sandy substates, which can lead to other issues. More on point though, you'll generally need a deeper bed of substrate for adequate dentrification. This is due to the fact that the larger particulate sized substrates allow more oxygen to penetrate deeper into the substrate.

In addition, I wouldn't recommend adding a layer of sand ontop of the current substrate. Eventually the smaller sand particles will descend and the larger shells will sift towards the surface. If you just want a sandy look to it, then you should remove a portion of your current substrate at a time and replace it with the sand. You might be able to get away with replacing the entirety at one time, but that depends on how much detrius has built up down there and the amount of toxic sulfide build up.

Personally, I used the finest grain sand I could find and my SB is only 3/4 to 1inch deep at the max. I've got plenty of dentrification going on, as there are tons of nitrogen gas bubbles right under the sand's surface. The negative of course is that without perfect flow positioning, I get a sandstorm .

 

[dakota9]

hmmm, lots to consider here...... Can I cover my exsisting shell bed with like 1/2 of not "live", new bagged carib sea sand tonight without killing off the bacteria in my substrate? I really dont want a shallow substrate, I'd prefer it be fairly deep, but I've got corals and anemones in this tank. As far as any crap build up, theres very little. I thoughly diatom every 3 to six months, this requires me to empty livestock out of the tank, mix the gravel up and put diatom filters in the 2 magnums that run on the tank, is this a bad idea as well? <note to self, "it's no longer 1988">

 

[xyzpdq0121]

FutureInterest;47016 wrote: I'm no expert by any means, but I'll impart what knowledge I have gleaned... The key to determining the necessary depth for a sand bed is the size of the particles that make up the substrate. The smaller the particles, the less depth you need to create an anaerobic zone for denitrification. As such, using the small shells, although attractive, have two drawbacks. First, you'll find that crushed coral and shell based substrate tend to trap detritius and particulate matter more than sandy substates, which can lead to other issues. More on point though, you'll generally need a deeper bed of substrate for adequate dentrification. This is due to the fact that the larger particulate sized substrates allow more oxygen to penetrate deeper into the substrate.

In addition, I wouldn't recommend adding a layer of sand ontop of the current substrate. Eventually the smaller sand particles will descend and the larger shells will sift towards the surface. If you just want a sandy look to it, then you should remove a portion of your current substrate at a time and replace it with the sand. You might be able to get away with replacing the entirety at one time, but that depends on how much detrius has built up down there and the amount of toxic sulfide build up.

Personally, I used the finest grain sand I could find and my SB is only 3/4 to 1inch deep at the max. I've got plenty of dentrification going on, as there are tons of nitrogen gas bubbles right under the sand's surface. The negative of course is that without perfect flow positioning, I get a sandstorm .

Ya what he said!!!

Dakota9;47019 wrote: hmmm, lots to consider here...... Can I cover my exsisting shell bed with like 1/2 of not "live", new bagged carib sea sand tonight without killing off the bacteria in my substrate? I really dont want a shallow substrate, I'd prefer it be fairly deep, but I've got corals and anemones in this tank. As far as any crap build up, theres very little. I thoughly diatom every 3 to six months, this requires me to empty livestock out of the tank, mix the gravel up and put diatom filters in the 2 magnums that run on the tank, is this a bad idea as well? <note to self, "it's no longer 1988">

Yes it is not 1988 anymore.... Jin, is right, mixing substrate is not a good idea without something to keep them from mixing (see the screen idea above) and even then, not the best idea. I LOVE DSB and understand why you want one. I bet you have more traped in those shells then you realize. IF YOU ARE GOING TO TRY TO ADD SUBSTRATE KEEP IT TO UNDER 1/4"... Sorry to yell but I wanted to make sure you heard me. This goes for anyone trying to add to their sand bed, not just in your case. any more then 1/4" at a time could change they dynamic of your sand (shell) bed too much and lead to very bad things. Again, if it was me, I would replace the entire sand bed with 1/2 bagged sand and 1/2 live sand from someone's tank breakdown.

 

[dakota9]

Thanks guys, I was going to try an attempt re-doing this substrate tonight, but will put it off until I can better figure out what is best to do. The shell bed has lasted on and off for 20 years, it should last another month or so, giving me time to figure out a good plan of attack, maybe one huge crap load of live sand. Thanks again, Dakota

 

[xyzpdq0121]

hehehe ya shell substrates worked and still do but there is much better science out there now that is lower maintance and offers much more stability. I think a substrate change is called for after 20 years!

 

[FutureInterest]

Welcome back Brandon. Hope you had a blast!

 

[siege]

I have a DSB in the tank I have been maintaining, as Jin can attest to - roughly 4" of aragonite on top of a plenum (about 1-1/2" high in itself) in a 50 gallon. I like the look of it, but at the same time it would be nice to have all that space to work with for aquascaping and fish movement... I also wonder sometimes if the DSB and</em> the plenum isn't sort of redundant, but then, my tank, regardless of other problems it might have had (3-day power loss = suck), nitrites/nitrates have ALWAYS tested zero.

 

[xyzpdq0121]

I used to run a plenum in my main tank years ago. They are great but you are right, it limits your space. I opted for a plenum in my fuge instead and a normal 3 1/2" DSM in my tank. Seems to have the best of both worlds.

 

[dakota9]

Thanks for all ya'lls advice! I'm looking into going with a plenum on my tank, it seems to be the best way to convert what I already have going. Now, get ready to disagree, but all the Plenum methods I've seen (egg crate propped up to 1 inch, covered with screen x2) is basically achieving the exact same as an undergravel filter would do (not hooking pumps up to the UGF of coarse, just capping off the out take tubes) then put 2 to 3 inches coarse substrate over undergravel filter, covered in turn with screen (x2) and finally a fine substrate. I've got the UFG from a previous fresh water set up. What obsticles does anyone see with this method? Thanks, Dakota(9)

 

[xyzpdq0121]

A UFG WITHOUT a pump would work very simular to a Plenum. The difference in the "void" space on a UGF is much less in most cases the a true 1". I have used a Plenum for about 10 years now and sware by them and the science behind them. My advice though, spend the $10 and make one out of egg crate. I can only assume here but the amount of open area in the squares of the egg crate would create much more gas exchange then the slits in most old school UGF.

 

[FutureInterest]

I honestly don't think plenums are necessary. They're designed to help reduce nitrates, but I would argue that a DSB or a SSB would be just as effective so long as the particle size is small enough. I've seen quite a few tanks with no SB or a SSB and have nitrate readings of 0. I think plenum's might've been a great answer for nitrate reduction back in the day... but now that skimmers are so much more effective they're really not necessary IMO. Why are you resisting the DSB?

 

[xyzpdq0121]

Jin could be right here.... I doubt I would have too much of a shift in chemestry in my tank if I took out the plenum in my fuge but I am not going to test his theory for him!

It does remind me though, I think plenum or not, you are going to inhearently run into more chemestry problems because of your partical size then anyother reason. I do not know if a plenum is going to help reduce that for you.

 

[dakota9]

the particle size of the shell is not all that large, and because of the half oval shape they have, they dont back down bad either. Maybe I'll just screen over the shell, and slowly add sand, dont think I'll do it all over the tank 1/4 inch at a time, think I'll do like 1/6 off the tank bed every 10 days until its covered. Sound like a plan? Thanks, Dakota(9)

 

[xyzpdq0121]

See if these two links shead some light on your situation:

Check out this link for a reference:

 

[dakota9]

Wow XYZPDQ... (i hate when you guys dont use a variation of your real name) I got so caught up in reading at WWM thank I almost forgot to that you for the link. I'm going to consider my options carefully before preceeding. Thanks again, Dakota(9)

 

[xyzpdq0121]

My name is in my signature... It is Brandon BTW...

 

[dakota9]

Yeah, sorry bout that, was up late last night posting to forum while drinking beer, sometimes the two dont mix! Thank you BRANDON!!!! Dakota

 

[matttvi]

In addition to brandon's links, here is some more stuff on sand beds by Dr. Shimek:

http://www.reefkeeping.com/issues/2003-06/rs/feature/index.php">Reef Central Article</a>

[IMG]http://www.ronshimek.com/Deep%20Sand%20Beds.htm">Shimek's Hosted Article</a>