how to cement together live rock that is already in establis

[drkat]

I have a 250 gal tank, free-standing with viewing from all foour sides. Unfortunately when live rock was put in, it was placed into a beautiful formation, but not cemented or otherwise attached. I now have periodic problems with rock falls from any number of causes: urchins bulldozing, diamond goby moving sand foundation and creating unstable sand base etc. Any good tips on how to secure the rock in a water environment??

 

[danmhippo]

Use underwater epoxy.

 

[jdieck]

As recommended use putty epoxy to join rocks together unfortunately that may not help with the unstable sand base.
To correct that if you are up to it you will need to start all over and empty your tank. Once empty use 2" PVC couplings as stands to set the rock raised above the tank bottom. drill 3 or 4 holes on the sides of the couplings to prevent stagnant water. Half fill your tank and use three couplings for each base rock (The larger the rocks the easier). Setup your rock pile on top of the base rocks gluing them together if you wish.
Once all your rock is set up raised above the bottom, fill the bottom with your wet sand use a small powerhead to "blow" the sand under the rocks until the couplings are totally covered. Now your gobby can dig happily as much as he wants and you will still have a stable pile.

 

[fishguru]

Actually if you are starting over, why not just aragocrete them together, as long as you dont use a HUGE amount, it should be fine, or people have drilled holes and used zip ties. Wouldnt be miy first choice, but they have done it...Brent

 

[epon]

Aragacrete has a long setup and cure time. Thorite doesn't. It's available locally to me at a cement company.

 

[rebornhunter]

I use Hold Fast by Marineland Aquarium Systems got it from LFS. U can check marinelands.com

 

[cdeakle]

Why do people always want to use a false bottom or risers?

If starting over all you have to do is put the rocks in first and then add the sand after. Fish and other sand sifters can move sand as much as they want and the rock foundation will still be stable because there is NO sand underneath them!

-puff

 

[Anonymous]

Why do people always want to use a false bottom or risers?

If starting over all you have to do is put the rocks in first and then add the sand after. Fish and other sand sifters can move sand as much as they want and the rock foundation will still be stable because there is NO sand underneath them!

-puff

I like to stack my rock relatively high up and against the back of the tank. I have found that the rocks may still slide along the glass bottom even if embedded in 5" of sand. To avoid this, I always include a plastic eggcrate shelf buried an inch or so below the top of the sandbed. I do not use any screening on top of the eggcrate so that critters can easily move throughout the sandbed. The grid pattern of the eggcrate provides a good anchor point for the base layer of rock, thereby increasing the stability of the entire rock structure. The eggcrate also keeps fish from burrowing too far into the sandbed. Note, this can be undesirable if you want to keep certain kinds of wrasses.

Once I am happy with the structure of the rock work, and I am sure that it is stable, I use 2-part epoxy (Home Depot sells this in the plumbing section for $5 per stick) to bond or reinforce key junctures between separate pieces of rock. This is typically done after the tank has been filled, but it doesn;t have to be.

I have used this techniqe without fail for numerous tanks from 2 gallons to 400 gallons.

 

[snotroll]

One thing that's important to remember when using underwater epoxy, or any adhesive: Make sure ot clean the area you're going to stick together, the epoxy wont do any good if it's just bonding to the bacterial/algae slime that covers your rocks.

use a new cheap toothbrush to clean a small area on each rock, right at the location you're going to attach them.