rock before or after sand?

[work765]

i heard from my LFS that i should put the rock down first then the sand around it, becasue if you do it the oppositte way(sand then rock) the weight of the rock will put presure on the sand and certain animals will not be able to live there.

anyone know the real truth?!!

 

[Anonymous]

put some pvc under the sand to hold the rock up. It is cheaper and takes up less space.

 

[fishfarmer]

How much sand are you putting down? 4" or so? I think putting the rock in first would be a waste of good rock. I've elevated the rock on both tanks I've set up. One was a shallow bed with a plastic pallet hidden under there. The other was a PVC structure elevating a very heavy slab of dead coral with LR covering up some of the PVC. I was concerned about the pieces of PVC in the sand creating dead spots and worried about critters falling into the PVC legs and not being able to get out so I cut the pieces in half lenghtwise.

My soon to be upgraded tank will have a 4" bed with the rock placed on the bed. I will probably support some of the rock with smaller pieces of rock and do some epoxying of the larger pieces, but I won't be too concerned about compacting because I've heard that it isn't too much of a concern. I wouldn't completely cover your sandbed though.

 

[rgardiner]

In researching DSBs, Ron Shimek advises to put the sand in first, then the LR goes in, well embedded into the sand.

 

[kcinminni]

If you put the rock on the sand (embedded or not), something will burrow under it and could topple the whole thing. Put some PVC pipe on the bottom like this OOOOOOOOO to make the rock sturdy. That way you're not hiding all of the rock, and if the burrowers go to town they will run into roadblocks.

 

[Anonymous]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by work765:
<strong>the weight of the rock will put presure on the sand and certain animals will not be able to live there.</strong><hr></blockquote>

I've heard that putting in the live rock and then adding the full 4 inches of sand could cause problems because there will be animals in that part of the rock that don't belong buried under 4 inches of sand and there will be die off.

Always double check what your LFS tells you here.

Good luck.

 

[kcinminni]

Of course! The LFS WANTS you to put the rock down first, then the sand. Then you have to buy that much more rock from them.

As Tangirl said--always double check what your LFS says--I've had to change multiple things. This forum can be invaluable.

 

[sparks]

I'd put the sand in first, them push your larger rocks into it just like Dr Ron Shimek advises
( agree with Roy ).
I don't think any PVC etc is neccessary, its just a waste of time IMO.
I don't think toppling rocks will be a real problem, maybe if you had a ray or wobbygong shark 2foot long or something.

 

[eodjj]

You're doing the right thing---asking questions, I have learned so much from this BBS...
Two points I didn't read above:
1. Most things that live in the sand, burrow by nature. (So you shouldn't hurt them, normally)
2. Use of PVC is dependent on the size of your tank. (Would look a little weird in some nano-reefs <20 gallon, but is invaluable in larger tanks where your rock is over a foot off the bottom. "Falling rock tends to break glass")
Just my 2 pennies.
JJ
Oops just noticed you're from Cali,
California=earthquakes.

[ March 22, 2002: Message edited by: eodjj ]</p>

 

[pez]

I have my rock on the sand and plenty of things burrow under the rocks. If the rocks are wide enough and your rockwork is generally stable, you will not have a problem. But if you have piers of rockwork, then something can topple it by displacing a rock or two. I think the PVC is not necessary if the rockwork is setup "correctly".

-Tom

 

[Anonymous]

If you buy large pieces of LR soo much of the rocks bottom will be in contact with the sand that burrowing will have no effect.

 

[M.E.Milz]

I have used this approach on all of my set-ups (reef and FO tanks with DSB's), and it has never failed.

1) Figure out how thick your sandbed will be. If 2" or more, then go to step 2. Otherwise, go to step 3.

2) Add a horizontal shelf of eggcrate (plastic light diffuser) at about 1" below the intended top of the sandbed. The shelf should span the the entire lenght and width of the tank so that it will not shift around. The shelf can be supported by pvc fittings (such as couplings) or pipe, or by additional strips of eggcrate placed on edge and cable-tied together.

3) Same as step 2, but place the eggcrate directly on the bottom of the tank.

4) Add the sand. Dead first, then seed with live sand (if you have any). Some have suggested burying a few pieces of shrimp in the sandbed to promote critter multiplication, but I have never tried this.

5) Add the rock. Start by pushing a few larger, irregularly shaped pieces (Tonga branch is great for this) into the sand unitl it rests on the eggcrate. The eggcrate will keep the rock from sliding around. And if you elevated the eggcrate (step 2), it will minimize the amount of rock that is buried. Now add the rest of the live rock to form a stable structure. Remember, as you add each new piece of rock, it should have 3 points of contact, either with other rocks, the eggcrate shelf, or the back wall of the tank. If done right, you will end up with 90-95% of your live rock above the sand.

Another nice feature of using the eggcrate is that it will permit critters to move throughout the sandbed, but will prevent fish from digging up all but the top layer of sand.

FWIW, both of these tanks were set up using this method.

Mike's reef tank & Mkie's office tank

[ March 22, 2002: Message edited by: M.E.Milz ]</p>