Building hollow rock

[Paul B]

I know there have been numerous threads on building rock, but I think I make it differently. I make it hollow so besides allowing me to make it any shape, it also helps grow anerobic bacteria that will help with nitrates.
My entire reef structure is supported on this type of "rock" and I can build rocks very long and thin, something that is not easy to build with other methods. It is also very cheap, practically free and only takes about 15 minutes over 3 or 4 days.
First I bend a piece of PVC pipe. "This MUST be done outside with the wind going away from you." Melted PVC fumes are toxic and will sicken you instantly. If you use a heat gun it is better as it will not char the PVC but I use a propane torch and it must be done outside. You do not want to sniff any melted PVC. Trust me.
I play the torch over the pipe until it softens, then I bend it in odd shapes and stick it in water. You need a hose near by because sometimes it may go on fire. If you keep the torch a distance away that will not happen but keep a hose ready anyway.
I use "Sakrete" cement.

Then I cut the bent PVC in the shapes I want it. These smaller pieces will be used to support my reef structure when I re aquascape shortly. The larger piece will be used to support a coral.

I attach a base of acrylic plastic. I use a stainless steel screw and thread it into the acrylic, then glue gun the head of the screw into the PVC. Some people are afraid of stainless steel so you can use nylon screws. I have holes drilled all over the PVC to facilitate water entry. When I stick the head of the screw into the PVC pipe, I just stick the glue gun into t lower hole and fill it with hot melt glue.
String is wrapped around the PVC and secured with hot melt glue. Then cement is mixed kind of loose, this is smeared all over the string (wet the string first, the cement will stick better)
You will get a thin coat of cement all over the thing, but you can not finish it all in one day.
Put a bucket over it and let it set for at least two days. Then blob on more cement and wait sanother 2 days. Neatness does not count and you want the cement blobbed on rather than smoothing it on. Eventually, you will have something that will look better than any rock you can buy and coraling algae grows much better on cement than it does on real rock. Cure it in some water for a few weeks before using in your tank.
Here I started to put cement on one piece. The shell on top will eventually hold a coral.

This piece (before and during construction is 3' long)

Here is another piece supporting my structure.

This "old" bottle was also constructed using cement.

Thanks, you can see one of those skinny rocks here above the copperband

You can see the larger rock here behind the moorish Idol and all the way to the left under the torch coral.

 

[revhtree]

Paul you're a wealth of knowledge my friend! Thanks for sharing!

 

[Paul_N]

Very cool! I like the idea of the area for the bacteria to grow.....1smile1

You know, the third pic down you posted could probably pass for modern art. You should submit it to a gallery...lol.

 

[Paul B]

the third pic down you posted could probably pass for modern art

Thats the look I was going for.:wink:

I built those shapes short mostly for this post but you can build this stuff as long and complicated as you like. You can attach diffferent sizes of PVC and bend it in all sorts of shapes, the wierder, the better. When you are building it, you can add places to place corals.
That piece I built with ther old oyster shell will be used to hold a coral or clam 10" off the bottom. When it is completed, it will look natural and you will not see the shell under the coral. I have structures like this all over my reef which gives it a "lacy" look instead of a pile of rocks.
Some of my hollow rocks are decades old, they hold up very well and grow colorful coraling algae very fast.

 

[Paul_N]

You're like the da vinci of reefing....lol

 

[Paul B]

You're like the da vinci of reefing

Thats because he is my Idol

 

[Paul B]

They are almost completed and now I can get creative by cementing on pieces of dead coral and making the surface rougher.
The shorter pieces are just going to be supporting columns for my reef structure when I get around to re aquascaping. This is how I keep the large pieces of rock off the substrait.

 

[nixer]

Thats because he is my Idol

he was pretty awesome. he was into everything!

those are some sweet pieces.

 

[Paul B]

Here is a piece that was in my tank for a decade or so

It kind of disappears in my tank

 

[Paul B]

The mandarin doesn't know this is fake