DIY rock

[tbrown]

I used Portland type 2 cement and oyster shells years ago. I slowly swapped it out for real rock but there are still a couple pieces in my system.
You never have to worry about po4 dropping off with oyster shells.
But sand will look much nicer. Maybe mix sand and shells?

This is a suggestion on several of the walk throughs online. Using either crushed coral/oyster shells and fine grain sand or multi sizes of sand.

 

[John K]

I think I spent $35 for th cement and sand - enough for 100+ pounds worth.

Where are you finding inexpensive reef sand these days?

 

[tbrown]

Where are you finding inexpensive reef sand these days?

I got mine on Amazon.

https://a.co/d/4wT161n

https://a.co/d/bK6sagA

This is the stuff I bought - currently out of stock though.

https://a.co/d/g9KfhZY

When it's in stock it's $12.00 for 20#.

 

[tbrown]

Well that didn't work.

 

[Paul B]

I remember reading about @Paul B doing something similar but making structures. My memory isn't great and I can't remember where I read it. May very well have been Paul's book that I read. They looked pretty cool.

It is in his book and here.

Build your own rock for practically free

Make your own rock When the hobby started there was no live rock for sale, as a matter of fact, there wasn’t even dead rock for sale. We used dead, white bleached pieces of coral to decorate our tanks and we bought that in a furniture store...

www.reef2reef.com

But I am not speaking to him.

 

[tbrown]

It is in his book and here.

Build your own rock for practically free

Make your own rock When the hobby started there was no live rock for sale, as a matter of fact, there wasn’t even dead rock for sale. We used dead, white bleached pieces of coral to decorate our tanks and we bought that in a furniture store...

www.reef2reef.com

But I am not speaking to him.

Good thing you're not speaking to him or they might recommend yet another type of specialist!

 

[John K]

I got mine on Amazon.

https://a.co/d/4wT161n

https://a.co/d/bK6sagA

This is the stuff I bought - currently out of stock though.

https://a.co/d/g9KfhZY

When it's in stock it's $12.00 for 20#.

Huh? I'm confused, if sand is $12/20 lbs, how do you make 100 lbs of rock for $35? Very high cement to sand ratio?

*not trying to nit pick, legitimately trying to follow here. My experience making rock was @ 20 yrs ago when aragonite (Southdown) could be had for $5 / 50 lbs. Still sounds like a good project, just trying to understand the current math / cost.

 

[tbrown]

Cement is cheap and I was using 2 parts cement to 1 part sand. I think I paid $4.50 per 50 pounds of cement.

 

[tbrown]

Even if it costs $1 per pound to make it's cheaper than purchasing dry rock at $3-$5 a pound and you choose the size and shape.

 

[John K]

Cement is cheap and I was using 2 parts cement to 1 part sand. I think I paid $4.50 per 50 pounds of cement.

Oh ok, that makes sense, thanks.

IIRC I used to use a much higher sand ratio. (Plus lots of extra sand for the sandcasting)

Definitely agree this can be a money saver.

 

[tbrown]

Oh ok, that makes sense, thanks.

IIRC I used to use a much higher sand ratio. (Plus lots of extra sand for the sandcasting)

Definitely agree this can be a money saver.

I started with 1:1 but it became crumbly when curing so I upped the cement.

 

[tbrown]

Pulled this one out of the sand just now.

This is supposed to be the bottom but may be the top...

This was the top:

 

[Paul B]

I use the same cement they built the Brooklyn Bridge out of. The stuff is practically free.
(I also used the water from under there, but don't tell anyone)

 

[tbrown]

I use the same cement they built the Brooklyn Bridge out of. The stuff is practically free.
(I also used the water from under there, but don't tell anyone)

Gotta be careful with Brooklyn bridge cement though, it might have bodies!

 

[Paul B]

Only Jimmy Hoffa.

 

[Katrina71]

Either way he sleeps with the fishes

 

[thrillreefer]

@tbrown or anyone, thoughts on building a mold to make rocks of a certain shape? E.g. I’m considering a nano for my desk at work and would want to make a rock in company logo shape, or write a word with flat rocks on the back wall, etc. Any considerations? Likely would 3D print the molds.

Did you ever add rock salt to make DIY rocks more porous? Leaves voids after it dissolves away. But supposedly might weaken the cement bonds also.

 

[tbrown]

@tbrown or anyone, thoughts on building a mold to make rocks of a certain shape? E.g. I’m considering a nano for my desk at work and would want to make a rock in company logo shape, or write a word with flat rocks on the back wall, etc. Any considerations? Likely would 3D print the molds.

Did you ever add rock salt to make DIY rocks more porous? Leaves voids after it dissolves away. But supposedly might weaken the cement bonds also.

I add salt crystals rather than rock salt because they're smaller pieces and cheaper than a bag of rock salt I believe. I think it was a 50+ pound bag of Morton Water Softener salt crystals for lik $5.

You can make the logo and even use purple primer to accent certain portions of the logo.

Making a mold was something I had considered but how do you keep it from sticking. Silicone might work?

 

[officialreefbros]

I went down this rabbit hole of looking into it a lot about a month ago. I saw the rock that was sold out of a WWC tank and loved the style but the guy who made it passed away and so did his recipe. This thread has a ton of good information: https://www.reef2reef.com/threads/diy-rock-tutorial-info-thread-rocks-walls-floors-etc.31971/

 

[thrillreefer]

Nice, will check that thread out!

Re: adhesion to molds, some plastics should be ok for easy release, so I can look into which filament types are available for printing then pick a safer one.

There are release agents to try if this doesn’t work, like mineral oil or paraffin wax. Would have to hope they can be washed off or diluted during curing. Info here