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.

[paul b]

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.

 

[jason the filter freak]

With the limited avaiability of tonga branch rock these days this is an awesome and attractive alternative.

[paul b]

When I spoke at your meeting a couple of years ago, I think I brought a piece of this with me.

[scott711]

darn work can't see the pictures

[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]

My mandarin doesn't know it is fake either

[dandy7200]

Heating PVC to the point of scorching (brown marks in your photos) produces chlorine gas and when it is mixed with moisture (in your lungs) produces hydrochloric acid (which can KILL you)! Added disclaimers in the future would be nice, 1.5" acrylic tube is very cheap considering the alternative. Cool rocks :-)

[faerieannette]

i love the rocks!!! genus! I think i am going to make some for my seahorse tank. where do you get the acrylic tubes, home depot? are they easy to drill? bend? where did i put my propane torch?...

 

-Annette

 

Heating PVC to the point of scorching (brown marks in your photos) produces chlorine gas and when it is mixed with moisture (in your lungs) produces hydrochloric acid (which can KILL you)! Added disclaimers in the future would be nice, 1.5" acrylic tube is very cheap considering the alternative. Cool rocks :-)

[paul b]

Heating PVC to the point of scorching (brown marks in your photos) produces chlorine gas and when it is mixed with moisture (in your lungs) produces hydrochloric acid (which can KILL you)! Added disclaimers in the future would be nice, 1.5" acrylic tube is very cheap considering the alternative. Cool rocks :-)

 

 

This is in the first paragraph of this thread.

 

"This MUST be done outside with the wind going away from you." Melted PVC fumes are toxic and will sicken you instantly.

 

where do you get the acrylic tubes, home depot? are they easy to drill? bend? where did i put my propane torch?...

 

 

I use PVC pipe from Home Depot. They are about $2.00 for 10' of 1/2" PVC

If you use a heat gun you will not have to worry as much of starting a fire or killing yourself but a torch can be used "OUTSIDE" with the wind going away from you.

[faerieannette]

I have a heat gun i got from the craft store and some cpvc and pvc lying around, even a bag of cement plus some beer. I am sure i can find some string somewhere. I know how i am gonna pend my evening. Sea Biscut needs a new hitching post and feeding station ;-)

 

-Annette

[LCDRDATA]

Timing is everything - I'm going to be setting up a new tank soon and remembered your presentation about this at a WAMAS meeting awhile back. I was was thinking about posting somewhere tonight to see if someone had the information as I could only remember the result. And here it is - thanks!

 

It would also help if you (or someone) could figure out how to make the pictures show up, but it's a good description even without.

 

A couple of other questions. First, do you build "large/thick" pieces with a single large-diameter pipe or a group (3-7) of small-diameter pipes wrapped together? Pros and cons of one method over the other? Also, we already have a good quantity of nylon (?) screening; would that work to wrap the tubes with as opposed to the string? Thanks again!

[faerieannette]

maybe a dumb question but would a piece of rock like this filter the water quality as effectively as solid rock of the same size? or perhaps more?

[paul b]

I sometimes use 3/4" pipe then connect some 1/2" pile then go to 3/8" acrylic tubing, it depends on what shape you want to make. You can use anything that you like.

I used to use PVC screening which is what I used at your presentation but I have found that cement sticks much better to string than PVC. I use a streing like a thick cotton. Plastic types of string are not as good.

I think the filtering capacity of this type of rock is much better than real rock just because of it's porosity and dead spaces inside. Don't seal it tightly but push some holes through the cement and into the holes in the pipe. Cement at that thichness is not water proof anyway and water will get in. I also leave some holes at the ends for water penetration.

But if it is better, I am just guessing.